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-
- ****************************************************************************
- TITLE Report on speeding up an Acorn A5000 computer
- AUTHORS Nick Smith <nas20@cus.cam.ac.uk> & contributors
- REVISION 0.07
- DATE 17-Mar-93
- DISTRIBUTION Electronic only - UseNet news
- COPYRIGHT (c) Nick Smith, 1993
- ****************************************************************************
-
- SUMMARY
-
- This is the initial version of my 'Guide to turbo A5000s', a detailed
- description on how to get an extra 5 MIPS speed out of a standard A5000 for
- peanuts (well ...) This document will eventually published in Archive
- magazine (I hope) but for now should be distributed in electronic form only
- - I want to get some feedback & correct some technical errors before paper
- distribution.
-
- It also contains a whole load of general RISCOS configuration advice, and
- possible hardware add-ons (speed related), which could be useful to owners of
- other Acorn computers.
-
- This document consists of ; SUMMARY
- INTRODUCTION
- PARTS & TOOLS
- HARDWARE MODIFICATIONS
- SCREWING & SOLDERING
- SOFTWARE CHANGES
- MORE SPEED?
- SPEED RESULTS
- USEFUL SOFTWARE
- FINAL COMMENTS
- SUPPLIERS
-
- INTRODUCTION
-
- With a 25MHz ARM3 and 12MHz RAM, the A5000 is a powerful computer (clocking
- about 13.5 MIPS - Million Instructions Per Second), but it is quite possible
- to increase this speed substantially without vast amounts of arcane
- knowledge & hardware skill. Before I describe some simple hardware &
- software modifications, you can have the obligatory warning :
-
- Certain of the (hardware) modifications described below are potentially
- dangerous to your machine, and they will a) certainly INVALIDATE YOUR
- MACHINE WARRANTY, and b) cause EXPENSIVE DAMAGE if not performed correctly.
- I except no responsibility for any damage or losses caused. This document is
- presented in good faith, and is subject to change without notice [read: full
- of mistakes]
-
- I honestly don't advise performing any of the hardware modifications unless
- you have used a soldering iron on a computer PCB before.
-
- Below I go into a fair amount of detail for those readers who (like me ;-)
- are not real hardware techies. For the dedicated hardware buff, here is the
- concise description of the hardware mods :
-
- 1. Desolder XTAL OSC 36MHz CMOS DIL [X2]
- 2. Desolder XTAL OSC 50MHz 14/0.3 DIL [X6]
- 3. Buy a selection of 38-72MHz replacement Oscillators
- 4. Buy 3 or 4 suitable IC heatsinks - fit to ARM3 [IC54], VIDC [IC9]
- and MEMC [IC41]
- 5. Try crystals in 38-60MHz range for [X2] until machine fails self-
- test
- 6. Try crystals in 52-72MHz range for [X6] until data aborts/address
- exceptions start occurring
-
- This gives a good speed improvement - possibly increasing the speed to over
- 18 MIPS.
-
- A good place for more detail on the A5000 internals is the 'A5000 Technical
- Reference Manual', which contains A0 size diagrams of the circuit board,
- lists all the parts, and discusses in depth practically everything
- hardware-wise about the A5000. At L65 it is expensive though.
-
- PARTS & TOOLS
-
- Tools that you will need for this job are few ;
- ---------------------------------------------
-
- 1. Small Phillips cross-head screwdriver (to get case off!)
- 2. Medium cross-head & flat screwdrivers (maybe)
- 3. Soldering iron (10-20W)
- 4. A solder-sucking tool
- 5. A steady hand, and (optionally) a friend to help out.
-
- Parts for this job ;
- ------------------
-
- Parts suppliers are listed at the end of the document.
-
- 1. 8 IC 'ferrules'
- I can't find these in the Farnell catalogue, but 2 of a 14 way
- 0.3" row spacing DIL socket should do as well.
- These are available from Farnell - [179-913] are 11p each.
- 2. 3 or 4 IC Heatsinks (4 if you want/have an FPA chip)
- A good passive heatsink is available from Farnell Electronics
- [175-006] at L1.82 each
- 3. Heat conductive adhesive
- Farnell [HTC10S] L1.45 for a 10ml syringe
- 4. Range of replacement Can Oscillators
- Advanced Crystal Technology supply standard and custom speed
- oscillators. You need 14 pin DIL, 0.3" spacing Crystal
- oscillators in the range 38-60MHz to increase the memory speed,
- and crystals in the 52-72MHz range for the ARM3 processor speed.
- ACT supply 40,42,45,47,48,50,54,56,57.14,60,64,66,72 MHz crystals
- at L3.00 each, and just about any other speed you could want at
- L12.00 (made to order)
- The exact number of crystals you buy is up to you - see below for
- advice on which ones to get, and remember that you will end up
- using only 2 !
-
- HARDWARE MODIFICATIONS
-
- The way different parts of the A5000 are controlled is quite involved.
- Below, Owen Smith (formally of Acorn Computers Ltd, now at SJ Research Ltd)
- details the timing system :
-
- Article 152 of comp.sys.acorn.tech:
- From: osmith@acorn.co.uk (Owen Smith)
- Newsgroups: comp.sys.acorn.tech
- Subject: Re: Hi res modes
-
- "On the A540 and all newer machines, the IO system runs at 8MHz and the
- memory runs at 12MHz. There are some synchronisation state machines to
- handle communications between the two, so you can vary the memory speed
- without varying the IO speed. The state machines just accommodate for the
- difference. You can run the memory at basically whatever speed you like
- within reason (providing it doesn't keel over and die) because the IO system
- is still running at 8MHz and the synchronisation logic adapts. Of course
- turning the memory clock up runs the RAM chips out of spec (and possibly
- some of the other components) so don't be surprised if your machine becomes
- unreliable.
-
- "The synchronisation logic is in the big bank of PALs on the A540 and issue
- 1 A5000s, it's in the IOEB chip in issue 2 A5000s and the A4, and it's in
- the ARM250 (along with the rest of the IOEB) on the A3010/A3020/A4000.
-
- "Where the IO and Memory clocks are derived from is a different issue. On
- the A5000 the Memory clock happens to share the 36MHz VIDC clock and the IO
- clock happens to share the 24MHz VIDC clock (both divided by three). On the
- A3010/A3020/A4000 all the clocks are derived from one master 72 MHz
- oscillator (except the 25.175 MHz VGA VIDC clock) so you can't change the
- memory speed without changing the IO speed. On the A540 I think the 12 MHz
- memory clock comes from a 72MHz oscillator, which is separate to the three
- VIDC clocks (but I may be wrong here). On the A4 everything comes from one
- master clock, because there isn't enough board space for anything else.
-
- "Fiddling around with these clocks is not advisable. It will invalidate your
- warranty and it may make your machine unreliable or break it completely. The
- above is provided as information to the curious only.
-
- Owen.
-
- The views expressed are my own and are not necessarily those of Acorn."
-
- Everything Owen points out is perfectly true - it WILL invalidate your
- warranty. I started hacking up my machine innards just before the warranty
- ran out ...
-
- So there are 2 main clocks we can alter - the ARM3 speed (which has its own
- 50MHz crystal, divide by 2 to give 25MHz), and the memory system which
- shares a 36MHz crystal with the video system. The I/O system is driven by a
- 24MHz crystal (also used by the video) and this shouldn't be altered !
-
- Changing the 36MHz crystal for a faster one will have a number of effects ;
-
- * Speeds up the machine overall (faster memory)
- * Increases the refresh rate of screen modes using the 36MHz crystal
- (less flicker on display)
- * Can mess up the timing of the rare (modern) game which uses a
- 36MHz mode, so the game would go slightly faster.
-
- If you increase the crystal sufficiently, then Mode 0 (and a few other low
- memory modes) will not display correctly on the monitor. Why this is is not
- clear, but it has been suggested that it is an obscure bug with VIDC.
-
- It is easy for me fix this because I have a PCATS graphics enhancer card,
- fitted with 24, 25.175, 32, 36, 40, 42, 45, & 47MHz crystals, and so I can
- software-select a PCATS crystal to override the altered crystal on the
- motherboard. If you have a PCATS card, then there is code inside my
- 'IconSwitch' module which provides this facility.
-
- A solution to this problem for non-PCATS owners would be to redefine bad
- system modes (0, 1, 4, 5 & 6) with a mode designer application to use the
- 25.175MHz crystal.
-
- In addition to redefining system modes, it is possible to software-switch
- the current system crystal by writing directly to the Video Control Latch.
- This is documented in the A5000 Technical Reference manual, and involves
- writing to address &3350048. The lower 4 bits of that byte hold the
- following data ;
-
- bit 0 VC0 } Clock speed, 0=24, 1=25.175, 2=36, 3=reserved
- bit 1 VC1 }
- bit 2 SP0 Horizontal sync polarity (0 +ve, 1 -ve)
- bit 3 SP1 Vertical sync polarity (0 +ve, 1 -ve)
-
- A5000 owners with an issue 2 PCB (which has an IOEB chip) can read from
- this address to get the existing state, while issue 1 PCB owners can only
- write to this address. A simple *MemoryA command can be used to write to
- the address and switch the system clock.
-
- A useful option for non-PCATS owners is to replace the 25.175MHz oscillator
- as well (used for VGA compatible modes) with a 36MHz oscillator (you can use
- the one you removed for the memory system). To actually make use of this
- oscillator, a modified version of Owen Smith's VIDCClock module (see USEFUL
- SOFTWARE) is required to select the (replaced) 25.175MHz oscillator whenever
- a 36MHz mode is used. Note that issue 2 PCB A5000s have a 2 pin crystal
- providing 25.175MHz (some have 25MHz) rather than a can oscillator. These
- can be desoldered and replaced with a 36MHz crystal, but must not be
- socketed (ie, they must be soldered straight on) because of the signal
- losses involved in a socket.
-
- The A5000 (at least mine - an issue 1 PCB) has 70ns RAMs fitted on the main
- board. However, most RAM upgrade cards use cheaper 80ns RAMs, and when I
- increased my memory system speed from 12MHz to 16.6MHz I found that the 2MB
- RAM card that I had from Craddock Computer Systems (now bankrupt) could not
- keep up. Because the chips were surface mounted there was little chance of
- me replacing them with faster chips, so I sold my existing card and got in
- touch with Simtec Electronics, who were only too happy to talk about high
- speed RAM cards. NOTE that I have no information about RAM card products
- from Simtec - this was purely a custom job that they did for me, and you
- should get in touch with them with your own requirements.
-
- I initially contacted IFEL Ltd about high speed RAM cards because of their
- higher profile (I had never heard of SimTec until someone on the net
- mentioned them in connection with combined ARM3/FPA upgrades). I must say
- that they were not particularly friendly, or indeed helpful - suggesting
- that 70 or 80ns would be 'quite suitable for my needs' when it was obviously
- not what I wanted. They do, however, sell A5000 RAM upgrade cards without
- RAM chips fitted.
-
- For various reasons to do with supplies of particular sizes of chip, I ended
- up with a vertically mounting RAM upgrade card from SimTec which actually
- contained 4MB of 60ns RAM chips ! By setting links appropriately, the card
- by-passes the 2MB of 70ns RAM on the motherboard. This cost very little more
- than a standard card and I am delighted with the results. Of course, if
- your 70ns RAMs can perform to the speed you want, it would be more
- economical to get a 2MB upgrade rather than a full 4MB of chips. Recently,
- Simtec have been in touch with me, and apparently they use high quality
- 70ns RAMs on their standard 2MB upgrade cards which can do 16.66MHz.
-
- I don't know how fast this card can go - there are a number of possible
- 'bottlenecks' - not just the raw speed of the RAM chips. In particular, the
- RAM card socket apparently gives an extra 5ns or so delay, and then there is
- the MEMC, and a whole host of other components. I don't have any suitable
- crystals over 16.66MHz to try in the memory at the moment. I have heard
- reports of standard 70ns RAM in an A5000 running at over 20MHz !
-
- Here is an important warning on increasing the memory speed (from a contributor
- who wishes to remain anonymous) ;
-
- To: nas20@uk.ac.cam.phx
- Subject: Re: ARM3 speeds on a 12MHz memory system
-
- "One warning I would give: back up your hard disc first, especially if
- you're messing with the RAM speed. You may find that the rest of your
- machine runs fine, but your IDE or SCSI interface doesn't correctly latch
- the data from the rest of the machine, and trashes the data on your disc.
- This happened to me when I was tweaking my 540; I lost the free space map,
- boot block, and root directory - as well as other bits - which made it kind
- of hard to reconstruct the disc. Fortunately I'd had the sense to make a
- backup...
-
- >Do you mean it could happen randomly with the machine running at a higher
- >speed, or is it due to the ARM3 falling over when it over heats ?
-
- "It's caused by raising the speed of the interface between the computer's
- memory and disc interface to the stage where the disc interface can no
- longer correctly latch the data it is being fed. The result is that it
- writes garbage to the disc. As I said in my earlier reply, if this corrupts
- vital parts of your disc's structure such as the free space map, boot block
- or root directory it means big trouble.
-
- "If you're running your machine outside spec something's got to give first.
- In the case of my machine it was this interface. I was running my memory at
- 16MHz, and had a machine that was seemingly perfect until I wrote to my SCSI
- disc. The problem was consistent, not intermittent, and had nothing to do
- with heat, or with the ARM3 falling over. It was just that the SCSI
- interface couldn't cope with the speed at which it was receiving data from
- my otherwise perfectly functional souped-up machine.
-
- "The moral is, if you increase the memory speed of your machine, watch out
- for disc corruption. In my case, bringing it down to 14MHz solved the
- problem.
-
- "If you want to try it good luck; but if it goes wrong, you've been warned.
- And there's plenty of things that can go wrong other than the disc interface
- packing in..."
-
- Now, in fact I have an Acorn SCSI card in use daily with an IBM MD3125A
- 128MB Magneto-Optical drive (fitted internally !) and have had none of these
- nasty corruption problems - it may be that running at exactly 16MHz can
- cause memory/IO synchronisation problems , or perhaps I have a particularly
- good SCSI card ... all these things are pretty much a 'Black Art' and you
- should be careful.
-
- SCREWING & SOLDERING
-
- To the actual job ...
-
- First take whatever static precautions you feel sensible - just touching the
- machine casing (when plugged in) should discharge any static, but you may
- want to use anti-static wrist straps, etc.
-
- Unplug all cables attached to the base unit, and clear yourself a level
- working area. Take off the case, and remove any podules & blanking plates
- from the machine.
-
- Removing the podule backplane (at the front of the machine, holding the
- harddrive and the floppy drive) is probably the trickiest part of the
- disassembly, so go slowly. First, a single retaining screw must be undone.
- This is located right near the front of the machine, to the right of the
- harddrive (looking down from the front & top).
-
- Next, unplug the cables leading to the harddrive and the floppy drive. The
- IDC data cables (the wide, grey ones) can be 'wiggled out' by gripping the
- sides of the black connectors and gently moving from side to side whilst
- pulling out steadily. Don't yank on the cable itself ! Make a note of which
- way around the cable went in before letting go - they have a thin red stripe
- on one edge to help. One of the most frequent mistakes that friends and I
- have made in the past is putting cables in the wrong way around!
-
- Before the backplane can be removed, one of the power cables to the main PCB
- must be pulled out (or at least in helps) There are a whole bunch of thick
- cables running out of the power supply - you want the red cable nearest to
- the backplane. It just pops off the top of the PCB by pulling gently
- upwards.
-
- The backplane is now lifted up - make sure you place your hands on the
- metalwork, and not on the hard or floppy drives. It may take a fair bit of
- force, and it can be helpful to have that friend hold the rest of the
- machine. Once removed, but it somewhere safe - you won't be doing any work
- on that part of the machine.
-
- Have a good look at the main PCB now, and do a quick sketch - identify the
- important chips ;
-
- * ARM3 CPU - square chip near the front of the machine. It has a crystal
- oscillator marked '50MHz' near it.
-
- * VIDC video controller - to the rear of the machine and on the left
- hand side.
-
- * MEMC memory controller - to the right of the machine, near the
- backplane socket.
-
- * Bank of 3 crystal oscillators - 24, 25.175 and 36MHz - near the centre
- of the PCB.
-
- Also, make a note of every connector that leads to the PCB, its colour and
- where it connects - now remove all the leads so that the PCB can be slid
- out. There should be the 6 power leads from the power supply, the power/HD
- leds and the speaker line. There are also quite a few screws that need
- undoing, and then the whole PCB slides out of the back of the machine.
-
- Now for the desoldering - hold the PCB vertically, and desolder the
- appropriate oscillators from the PCB. This is best done by have one person
- on the soldering iron, and the other gently pulling the oscillator out of
- the hole as the solder is heated up. The oscillators to be removed would be
- the 50MHz, 36MHz and the 25.175MHz (if you want to socket it for trying
- different video speeds for instance). ** Note the orientation of the
- crystals before you remove them. **
-
- Make sure that the holes are free of solder by using the solder sucker: one
- person heats the hole with the soldering iron, whilst the other gets ready
- to suck out the solder from the other side.
-
- Next - fitting the ferrules or crystal sockets. This should be relatively
- easy, just solder them in as any other component - just be very careful
- where the solder goes !
-
- Once you have successfully soldered in the ferrules/sockets, then replace
- the old oscillators (if you managed to avoid burning their legs off!), and
- rebuild the machine. It is rather annoying that the podule backplane/ hard
- drive get in the way of the ARM3 oscillator, so leave that off - the machine
- will still run. Also, don't attach any expansion cards (RAM or otherwise) -
- just put enough of the machine together so that you can load speed trial
- software off the floppy drive (eg, !ArmSI - see USEFUL SOFTWARE)
-
- Do a quick check of the leads to make sure everything seems connected
- correctly, and you are ready to switch on. Hopefully everything will work
- fine as before - the computer will probably complain about the lack of a
- hard drive, etc. but you should be able to go into the desktop and run
- software off the floppy drive.
-
- If things DON'T work, then the first thing you should look for is the
- power-on test failing. Below is a brief summary of what can happen (taken
- from the comp.sys.acorn FAQ list, maintained by Philip Banks).
-
- Subject: Comp.Sys.Acorn FAQ List Posting (Automatic)
- Date: Mon, 1 Mar 1993 00:00:21 +1300
- From: banksie@khantazi.welly.gen.nz (Philip R. Banks)
-
- "The purple screen at power on indicates that the self-test has begun. A
- brief ROM, RAM, VIDC and IOC test is performed and then the screen colour
- changes to blue and a full memory test is performed, along with a second
- test of the VIDC and IOC. When the screen returns to purple, the machine is
- testing for an ARM3. At the end of this sequence the screen colour is set
- to green (for pass) or red (for fail). If the tests have all passed then
- the machine starts to boot and the RISC OS 3 welcome screen is displayed.
-
- "If any test fails, the screen will remain red and the disc drive light
- will blink a fault code. A short flash is used to indicate a binary '0' and
- a long flash indicates a binary '1'. The bits are grouped into eight
- nibbles (blocks of four bits) with the most significant bit first.
-
- "The lowest seven bits are a status word. The meaning of each bit is
- given below in hex :-
-
- 00000001 Self-test due to power on
- 00000002 Self-test due to interface hardware
- 00000004 Self-test due to test link
- 00000008 Long memory test performed
- 00000010 ARM 3 fitted
- 00000020 Long memory test disabled
- 00000040 PC-style IO world detected
-
- "Bits 8-31 indicate the fault code and are described below. Not all the
- bits are used.
-
- 00000200 ROM failed checksum test
- 00000400 MEMC CAM mapping failed
- 00000800 MEMC protection failed
- 00004000 VIDC Virq (video interrupt) timing failed
- 00008000 VIDC Sirq (sound interrupt) timing failed
- 00020000 RAM control line failure
- 00040000 Long RAM test failure
-
- If nothing happens to the screen or drive light, then switch off, and check
- leads again. If nothing seems to fix your problem, then consult with an
- expert (not me!)
-
- Assuming everything has gone well, then you can now experiment at different
- speeds. The way I did it, was to purchase a range of standard oscillators,
- and starting from the standard system speed, increase in 2MHz jumps until a
- self-test failure occurred. You may like to take speed measurements at each
- stage using something like !ArmSI. As practical guide, you should be able to
- run your RAM at 16-20Mhz (x3 = 48-60MHz oscillator) and the ARM3 at 30-36MHz
- (60-72MHz oscillator).
-
- As far as failure modes go - it is generally fairly obvious when you are
- running the chips too fast. With memory, if you over-do it, the machine will
- fail its selftest when you switch it on (flashing floppy drive light, or
- nothing at all). Switch off *immediately* - certainly within 15 secs of
- power on. When you are right on the edge of the possible performance, then
- things may start to overheat - you can check with some sort of thermometer
- probe - good multimeters can measure temperatures, or you could use adhesive
- temperature indicator strips. An expensive solution is to use 'Spectratherm'
- fluid such as Farnell [175-644] at L23 for a bottle of the fluid which can
- be painted onto a surface and changes colour with temperature.
-
- The failure modes of an ARM3 chip are more tricky - it will fail to startup
- if going too fast of course, but right on the edge it will give rise to
- 'random' address exceptions or data aborts. I found that with no heatsink
- fitted, I got an unexplained (non-fatal) crash once an hour at 30MHz, and
- every 5 minutes or so at 32MHz. Fitting the heatsink meant I could run at
- 32MHz with no crashes. It you are worried about damaging the ARM3 by running
- it too fast - a) check the temperature over a couple of hours, making it
- sure it isn't overheating, and b) run a couple of MHz *below* what you think
- it runs reliably at. For me, that would mean using the 30MHz crystal rather
- than the 32MHz one - just to be on the safe side.
-
- SOFTWARE CHANGES
-
- Tuning the most speed out a system takes quite a lot of effort - it depends
- greatly on the system setup in question, and what it is used for.
-
- System startup - so who hates the length of time it takes to get from
- switch on to the desktop? Well, there are a number of things that can be
- done - it helps if you have a hard drive of course.
-
- A new setting in the CMOS RAM lets you disable some of the more lengthy
- tests performed at system startup (the 'self test'). It is best to leave
- these enabled until you have a completely stable system - if you have dodgy
- RAM you want to know about it!
-
- Bit 7 (0-7) of byte &BC is 'Hardware test disable' and when set to 1 will
- disable long tests at power up. Because this CMOS byte has other uses, it
- is important to set it correctly with an OS_Byte call. eg,
-
- REM Toggle state of Hardware test disable bit in CMOS
-
- REM Read byte
- SYS "OS_Byte",161,&BC TO ,,byte%
- REM EOR byte with mask for bit 7
- byte% = byte% EOR 1<<7
- REM Write byte back again
- SYS "OS_Byte",162,&BC,byte%
- END
-
- Another source of annoyance is the Acorn 'RISC OS 3.1' screen. Apart from
- getting heartily sick of seeing it day after day for months, it takes a
- second or two to display - especially if you don't have a font cache setup.
- During starting up, the desktop broadcasts a service call message;
-
- Service_DesktopWelcome (&7C)
- On exit, R1=0 to claim and stop startup screen from appearing.
- It should be claimed if you want to replace the startup screen, or to
- prevent it from appearing.
-
- A small PD module called 'Startup' written by Brian Brunswick claims this
- service call. Below is a UUencoded copy of the module, which can be decoding
- using '!UUDecode' or '!SparkFS', eg.
-
- --
- table
- !"#$%&'()*+,-./0123456789:;<=>?
- @ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_
- begin 644 Startup
- MV )0 "\ P !P D 1P %-T87)T=7 4W1A<G1U< D)a
- M,2XP,2 H,S @3V-T(#$Y.3$I(&)Y($)$0@!3=&%R='5P #, a
- M !D "I3=&%R='5P('!R979E;G1S('1H92!2:7-C3W,@,R!S=&%Ra
- M='5P('-C<F5E;BX ! +>D ()SD RXP, !H& *#C!#"@XQX N\ ((SDa
- H L"@X0" O>@.\*#A? QXP 0H ,.\*#A $ MZ0# G.0 @+WH$0 [^\ a
- a
- end
- --
-
- If (for some perverse reason!) you like the Acorn startup screen, then
- configuring a 32Kb font cache, plus pre-caching the fonts will give a useful
- speed up. RISC OS 3 has *SaveFontCache and *LoadFontCache commands, which
- can be used to save your most commonly used fonts (for instance the ones
- used in the TaskManager 'Info' dialogue box and startup screen) into a
- single file. You load this in your hard disc !Boot file before entering the
- desktop to speed things up a little.
-
- Opening directories - directories with many applications takes ages to open
- - even with a fast hard drive. To speed things up, you can stop the
- applications from filer booting (and hence from loading their !Sprites
- files) by holding down the CTRL key before entering the directory. Also,
- correctly partitioning your applications into a logical hierarchy - Apps1,
- Apps2, Music, Tools, etc. is always recommended. You shouldn't really have
- more than 20 apps in a single directory.
-
- Miscellaneous - all the usual speedups - configuring a bigger ADFS/IDE/ SCSI
- buffers & dircache setting, using a lower res mode with fewer colours, etc.
- all speed things up. Many magazines have carried articles on how to go about
- all this.
-
- ROM access speed - if you have the RAM to spare, then *RMFaster'ing
- important modules such as WindowManager and BASIC are worth while because
- they run faster in RAM than from ROM.
-
- The MEMC chip in the A5000 has 4 ROM access speed settings. When switched
- on, the operating system picks one (rather pessimistically) based on memory
- speed (eg, 12MHz). You can override the ROM access speed to run things
- faster using the following program;
-
- REM Speed up ROM access
-
- REM speed%=3 is the fastest, 0 the slowest. NB speed%=3 is likely
- REM to cause a machine crash with RISC OS 3 ROMs.
- speed%=2
- SYS "OS_UpdateMEMC",speed%<<6,&C0
- END
-
- When you are trying this, make sure you have dismounted any discs, etc. and
- have no unsaved work. Running ROMs too fast will crash the machine, but not
- do any harm - just reboot.
-
- MORE SPEED?
-
- If the speed achieved is not sufficient to satisfy (!) there are of course
- always additional hacks - some rather expensive. First, the processor:
-
- The A5000 has a 25MHz ARM3 CPU in a plastic quad flat pack (PQFP). As has
- already been mentioned, VLSI Tech. do not speed select their chips, and so
- it is always possible to get the chips to go faster than specced. For more
- speed, the passive heatsink described above could be replaced with some
- active device that gives better cooling.
-
- An example active 'heat pump' are thermoelectric modules (as sold by Farnell
- [105-941]) that work on the Peltier effect to pump heat from a hot surface
- (CPU) to a cold surface (machine casing ?) These require a power supply
- which could be taken from the Arc's internal power, and some heat conductive
- glue such as epoxy bonding or heatsink compound. These are very effective,
- but start at L10 and require a fair current (0.5 - 1A).
-
- Another solution is to mount another fan inside the A5000, blowing across
- the CPU to aid in cooling (perhaps in conjunction with the passive heatsink)
- A 40mm low voltage DC fan (suitable for driving from Arc power supply) such
- as Farnell [151-073] is L15.95
-
- For experimentation, a freezing aerosol (Ozone friendly of course!) which
- cools components to below -50C is useful to see how fast a chip can be
- driven is sufficiently cool enough. WARNING: I don't think running chips
- *way* over their spec is a particularly smart move - especially as the ARM3
- on the A5000 in surface mount, and so cannot be simply replaced if it is
- damaged. VLSI give the absolute maximum temperature rating of the ARM3 to
- be: -10C to 80C running, and -65C to 150C storage.
-
- Matthias Sattler <@uni-kl.de:m_sattle@poker.informatik.uni-kl.de> in
- Article 10 of comp.sys.acorn.tech, says:
-
- "I used 60 Mhz VIDC frequency in my A5000 and it worked quite well with
- 1024x768x16x60Hz. And even the normal A5000 monitor did it. But I have one
- BIG problem, the VIDC is too slow for that. Meaning I have to cool it all
- the time using cooling-spray ("Kaeltespray" in german but I think you'll
- understand what I mean) because the silicon based microchips are fastest at
- about 0C."
-
- He also says that cooling the VIDC chip increased performance, but the ARM3
- could not be speeded-up even with cooling-spray. I found that a simple
- passive heatsink *did* allow a worthwhile increase in ARM3 clock speed.
-
- One of the problems with the A5000 ARM3 is that it is in a plastic package -
- bad for heat conduction. Apparently, there were an early run of some 400
- ARM3s which were in ceramic packaging and specced to run at 35MHz !
- Unfortunately, Acorn never used these in production machines.
-
- Paul Gee in Article 1850 of comp.sys.acorn, says:
-
- "The 36Mhz ARM 3's are being produced by Ground Control Electronics. The
- story goes that Acorn once ordered a batch of 35Mhz ARM 3's from VLSI and
- then changed their mind. Hence roughly 400 35Mhz ARMs were made. Ground
- Control have got their hands on about 200 of them and are running them at
- 36Mhz."
-
- Robert Voisey <r_voisey@csd.uwe.ac.uk> in Article 1879 of comp.sys.acorn,
- replies:
-
- "Ground Control strongly implied that the chips would 'probably' run much
- faster than their rated 36Mhz. Speeds of up to 40 or even 42Mhz were
- suggested.."
-
- Speaking to the engineer at Simtec Electronics, he said it was entirely
- possible to desolder the existing ARM3 in an A5000, and socket one of the
- ceramic ARM3s in its place. Of course, this costs money - probably over L100
- (with the cost of a ceramic ARM3 on top of that), and you have to find a
- source of a ceramic chip too - Ground Control may well have sold out by the
- time you read this.
-
- Another possibility is to replace the ARM3 with another chip entirely -
- namely the ARM600 from ARM Ltd. Atomwide/Aleph One announced in a 1992 issue
- of BBC Acorn User magazine that they intended to produce a plug in card with
- an ARM600 chip on it - to replace an existing ARM3 or ARM2 CPU. This would
- give a good speed increase for ARM2 owners (with 8Mhz memory) because the
- ARM600 contains a write-buffer to effectively increase memory speeds, but
- is unlikely to give major performance gains over an ARM3. There are also
- significant incompatibility problems with the ARM600 and RISC OS 2.00/3.10.
- It will not be a cheap or simple upgrade to produce (IMHO).
-
- A more promising hardware upgrade for A5000 owners is the much talked-about
- FPA (Floating Point Accelerator) chip upgrade.
-
- John O'Malley <J.Herbert1@lut.ac.uk> in Article 2104 of comp.sys.acorn, says:
-
- "ARM Ltd made an official statement to the Electronics Times (or so the
- article said). It made no promises for silicon but said that it would be
- available 'early in 1993'.
-
- They also said that the chips would cost about #40 going down to around #30
- for thousand orders. This means that for A5000 and A540 owners, they should
- be quite cheap as all that it needed is the chip + a software patch. This is
- also true about owners of the new ARM3 + FPA socket upgrades."
-
- The A5000 has a socket waiting for the FPA chip, and so all is required is
- the chip itself, and some support software (which will no doubt be available
- from Acorn in some way) So a price of L50 - L100 for the upgrade could be
- imagined - giving fantastic performance increases in floating point
- operations, from about 80 KFLOPS (Thousand floating point operations per
- second) to over 3 MFLOPS (Million FLOPS) ! Of course, many applications will
- not benefit from such an upgrade since they use almost no FP ops.
-
- High bandwidth screen modes are quite a drain on even a 16MHz memory A5000.
- At the 1992 BAU Show, a number of companies announced their graphics
- enhancer cards which speeded up and enhanced the A5000's graphics
- performance. As well as providing more colours, higher resolutions and a
- decent palette, the important thing that some cards offered was on board
- video RAM.
-
- For instance, the Computer Concepts 'ColourCard' contains 512K of dual
- ported video RAM directly mapped into the Acorn video memory. An on-board
- Inmos video controller outputs video from the card at 60Hz or 70Hz - giving
- a flicker free display, even if the 'real' refresh rate by MEMC is only
- 10Hz. In this way very high resolution modes can be used with hardly any
- drain on the A5000 data bus (like running software in Mode 0) - giving
- impressive speed increases.
-
- These cards tend to cost at least L200.
-
- On the far horizon (at the time of writing), are upgrade boards which use
- the new ARM Ltd VIDC20 chip. An upgrade using one of these chips to its full
- use would far outperform any of the existing video cards for the Archimedes
- at a realistic price. Some of the VIDC20's specs ;
-
- * Full compatibility with VIDC1 video & sound modes
- * 1,2,4,8,16 & 32 bits/pixel modes (24 millions colours)
- * hires mono modes at 400MHz pixel rates
- * colour modes at 80MHz, 80MBytes/s bandwidth
- * CD compatible IIS serial interface (eg, 16-bit stereo sound at 44KHz)
-
- Some example modes (with on board video RAM) would be 1024x768 at 16bpp
- (65,000 colours) or 800x600 at 24bpp (24 million colours).
-
- Also, since Acorn are looking at integrated these chips in 'future
- products' there is going to be some real support in future operating
- systems.
-
- If you remember, in an earlier section, Owen Smith mentioned some
- 'synchronisation state machines' to deal with the memory and IO running at
- different speeds. It has been suggested by a couple of people that the
- logic used is not the most efficient possible in the case of memory at 16MHz
- and IO at 8MHz. If the synchronisation logic could be reprogrammed then a
- large increase in IO performance (SCSI disc speeds for instance ?) could be
- obtained. This would only be possible in issue 1 A5000s and A540s where the
- logic is contained in PALs rather than the custom IOEB chip used in later
- machines. This particular speedup is highly speculative and I have heard of
- no one who has tried it !
-
- SPEED RESULTS
-
- Below are some brief speed results, obtained using my !ArmSI application,
- for more detailed results, have a look in the 'Examples' directory supplied
- with the application.
-
- Don't read *too* much into the figures below - I haven't specified whether
- there was any video DMA, or the ROM speed, etc. Look at the files
- themselves.
-
- File Description MIPS FLOPS Dhrys
- ============================================================================
- A310 Original 1MB A310, RISC OS 2.00 4.76 22506 5988
- A440/1_std A440/1, RO3.10 4.83 16463 4500
- A440/1_287 A440/1, RO3.10, RMFaster FPE 2.87 4.83 22228 4496
- A440/1_280 A440/1, RO3.10, RMLoad FPE 2.80 4.83 24427 4500
- A3020 4MB A3020, RISC OS 3.10 7.23 34724 8390
- A500 A500, RO3.1, 20MHz ARM3, 12MHz RAM 11.44 69177 16556
- A4 A4 portable, RO3.1 12.85 77303 18181
- A5000 A5000, RO3.1 13.73 80446 19084
- A5000s Tests with RAM MHz/ARM Mhz/Video|NoVideo
- ============================================================================
- A5000i A5000, RO3.1, 32MHz ARM3, 16.6MHz RAM 18.01 108663 25252
-
- USEFUL SOFTWARE
-
- Some useful software to have when doing speed trials is (from the Newcastle
- info-server) ;
-
- 30/Apr/91 2 memc_roms speedup rom access
- 03/Mar/92 9 vidclock software control of turbo VIDC hardware
- 22/Jan/92 38 si arc speed indexer
- 19/May/92 20 startup multitasking boot-up, v0.04
- 27/Nov/92 140 armsi ARM speed indexer v3.31H
- 15/Feb/93 14 iconswitch low/high res icon utility v 1.00
-
- I would particularly recommend !ArmSI (because I wrote most of it!) as a new
- and much enhanced version of !SI which gives you lots of helpful speed
- indices for processor, video, floating point, BASIC, etc.
-
- FINAL COMMENTS
-
- Don't be too put off by all the warnings and horror stories above !!!! You
- have to be careful, yes, but if you really feel you have to have that extra
- speed ... I have run my machine happily (touch wood) for about five months
- now without any ugly problems occurring. Matthias Sattler has also run his
- machine out of spec for over 10 months with no problems.
-
- I would greatly appreciate any comments/corrections/improvements that you
- can add. In particular, if you carry out the mods, some scanned photos or
- drawfile diagrams would be great, as I want to put together a nice
- Impression document version of this.
-
- Oh - and GOOD LUCK !
-
- SUPPLIERS
-
- Farnell Electronic Components Ltd
- Canal Road, Leeds, Yorkshire. LS12 2TU
- Tel 0532 636311 Fax 0532 633411
-
- Farnell require you to set up an account before ordering (can be done at the
- same time as ordering I believe - contact them for more details)
-
- Advanced Crystal Technology
- Unit 9 Kingfisher Court, Hambridge Road, Newbury, Berkshire. RG14 5SJ
- Tel 0635 528520 Fax 0635 528443
-
- ACT have a minimum order of L25.
-
- Simtec Electronics Ltd
- Avondale Drive, Tarleton, Lancs. PR4 6AX
- Tel 0772 812863 Fax 0772 816426
-
- Norwich Computer Services
- 96a Vauxhall Street, Norwich. NR2 2SD
- Tel 0603 766592 Fax 0603 764011
-
- NCS generally require you to subscribe to their magazine before selling you
- anything! Well worth the money of course - you recover the cost of the subs
- in discounted prices, and the magazine itself is pretty good !
-
- Computer Concepts Ltd
- Gaddesden Place, Hemel Hempstead, Herts. HP2 6EX
- Tel 0442 63933 Fax 0442 231632
-
- Ground Control Electronics Ltd
- Unit 7, Kingfisher Court, Hambridge Road, Newbury, Berkshire. RG14 5SJ
- Tel 0635 524008 Fax 0635 528115
-
- IFEL Ltd
- 34 Culver Road, Saltash, Cornwall. PL12 4DR
- Tel 0752 847286 Fax 0752 840029
- -
- Nick Smith, Rm.226, Churchill College, Cambridge XOX Email: nas20@cus.cam.ac.uk
- Intel? Watashi o warawasenaide kudasi ... OXO or: nas20@uk.ac.cam.phx
- -
- DISLCAIMER: All views expressed are my own (or those quoted) and not
- necessarily those of any organisations that we work for or have worked for
- in the past. I have no direct connection with any of the companies mentioned
- in this document.
-
-
-
-
-
- From: rogersh@ccs.mt.nec.co.jp (Rogers Huw)
- Newsgroups: comp.sys.acorn
- Subject: 30MHz A5000 - How to do it
- Date: 18 Mar 93 03:24:22 GMT
-
- Well yesterday I wandered into Akihabara and picked up a 60MHz
- crystal for 800 yen (4.50 pounds), deciding to replace the 50MHz ARM3
- crystal with the 60MHz one. (The ARM3 is clocked via a divide-by-2 IC.)
- You need a standard 4 pin crystal.
-
- BTW Originally all ARM3s were rated at 30MHz. Due to VLSI deciding rather
- arbitrarily that the fabrication yield at 30MHz was a few % too low (they
- were chucking too much silicon back into the process), they downrated it to
- 25MHz. Fact is they probably would of made more money by leaving the ARM3's
- MIPS rating higher and accepting the lower yield - however that's
- another story.
-
- Thus the first few A5000s were shipped with 60MHz crystals, and 90+% of
- ARM3s will work without any problem at 30MHz.
-
- Well the actual replacement operation is not simple. For those
- interested in doing this, here is what I did. For newbies who aren't
- used to hacking the internals of their valuable consumer durables,
- I've included various precautions which all the _real_ _hackers_ (tm)
- out there can ignore... ;-) Note you need (obviously) screwdrivers,
- pliers, wire clippers (maybe a thin bladed scissors - see later),
- soldering iron, and solder.
-
- First get a large sheet of kitchen foil, put it over your work
- surface, solder some green earth mains cable to it, and attach the
- other end to the earth pin from a UK mains plug. Plug this earth pin
- into the mains earth. Alternatively use a croc clip on the cable to
- attach it to a large steel desk/radiator. This is to earth everything
- (including you) and prevent static electricity damage.
-
- Place the machine to one side of this cover. While you work on the
- machine, regularly touch the foil. The last thing you want is static
- damage. Ensure you have enough space for three machines on the foil.
- Put the machine at one side of the space with the rear facing inwards.
-
- First you have to completely disassemble the machine. I.e. remove the
- case, any expansion cards, and backplane - keep them all on the foil.
-
- Then unplug all cables leading to the motherboard. I.e. the PSU cables,
- and the LEDs. Then unscrew the motherboard's connector plane from the rear
- of the machine and slide the whole board out the back. If you have a
- 4/8Mb upgrade you will need to remove the blanking plate above the
- motherboard's connectors in order to get it through the gap.
-
- Place the motherboard somewhere well lit and easy to access. If you
- have a memory upgrade fitted (especially if you have 8Mb), then
- place a support under the PCB where the upgrade connectors are. When
- refitting the upgrade it can require some force to insert the connectors
- and you don't want to flex the PCB unnecessarily - alternatively you
- could remove the spacers from the underside of the motherboard.
-
- I have the Atomwide 8Mb upgrade and this plugs into a MEMC socket as
- well as the standard connector. Be aware that unplugging the Atomwide
- memory upgrade involves violating your warranty.
-
- The crystal you need to remove is on the bottom edge of the motherboard's
- PCB and is marked 50.000 MHz. Unfortunately it is soldered flush with the
- PCB and it is very difficult to get at the legs with wire clippers. The
- solution I used was to use a pair of thin bladed scissors and a pair of
- pliers - slide the blades under the xtal to either side of each leg. Then
- apply the pliers to the portions of the blades not under the component
- to squeeze them together and cut the leg. You need to do this for all
- four legs.
-
- Once removed, place your new 60MHz crystal where the old one was. Do not
- clip the legs! It makes it much easier to solder if it is standing
- well clear of the PCB. Even tall legs will not cause problems with
- the memory upgrade (which sits quite some distance above the PCB).
- The orientation of the crystal is important. The dot on the crystal has
- to be at the same end as the indentation on the PCB drawing.
-
- Don't try to place the legs directly on top of the existing solder
- spots. Place the component so it is standing balanced on all four legs,
- with all the legs adjoining the solder spots.
-
- Now solder the legs to the PCB. This should be done quickly as excessive
- heat may damage adjoining components. The solder should flow nicely from
- the legs to the solder spots.
-
- Once the new crystal is installed, reassemble the machine to the minimum
- state necessary to boot it successfully. I.e. reassemble memory upgrade,
- backplane, and PSU cables. Then perform a test boot. If all is ok (run
- a few programs), power down and reassemble the rest. If the machine
- doesn't work any more, check your soldering and the orientation of the
- crystal. If it still doesn't work, go back to 50 MHz. If it still
- doesn't work - panic 'cause you screwed up somewhere along the line.
- In case you didn't take note when disassembling, the PSU cables are color
- coded as follows: Y - 12V, R - 5V, B - 0V.
-
- When fully reassembled, enjoy your 20% increase in CPU performance!
-
-
- From: rogersh@ccs.mt.nec.co.jp (Rogers Huw)
- Subject: 30MHz A5000 - How to do it - Supplement
- Date: 18 Mar 93 08:16:31 GMT
-
- >Once the new crystal is installed, reassemble the machine to the minimum
- >state necessary to boot it successfully. I.e. reassemble memory upgrade,
- >backplane, and PSU cables. Then perform a test boot. If all is ok (run
- >a few programs), power down and reassemble the rest. If the machine
- >doesn't work any more, check your soldering and the orientation of the
- >crystal. If it still doesn't work, go back to 50 MHz. If it still
- >doesn't work - panic 'cause you screwed up somewhere along the line.
-
- It just occurs to me that there is another possibility here. Try spraying
- all connectors you have detached with contact cleaner and then reinserting
- them. Liberal spraying of contact cleaner is, in any case, always a good
- idea and can never do any harm. It's worth ensuring that the memory upgrade's
- connectors are thoroughly clean, especially if you had to touch them. Sweat
- and grime can be very effective current inhibitors.
-
- _ _ _ _ _ _
- \_ \_ \_ \_ \_ \_
- _ _ _ \_ _ _\_ \_ \_ \_ \_
- \ \ \ \_\ \ \_ \_ \_ \_ _ \_
- \_ \_ \_ _ _\_ \_ \ \_
- \ \ \ \ \ \ \ \
-
- [ Huw Rogers Communications Software Engineer, NEC Corporation, Tokyo, Japan ]
- [ Email: rogersh@ccs.mt.nec.co.jp Fax: +81-3-5476-1005 Tel: +81-3-5476-1096 ]
- [ ]
- [ Disclaimer: This has nothing to do with NEC. Nothing at all. ]
-
-
-
- From: pgut1@cs.aukuni.ac.nz (PeterClaus Gutmann )
- Subject: Re: Turbo A5000 posting (long)
- Date: 20 Mar 93 09:22:41 GMT
-
- >Does anyone actually know what speed specifications the chips are
- >actually designed to run at, ie. by how much is running them at 12MHz
- >pushing them past their designed limits?
-
- (This is actually more relevant to the previous posting about speeding up
- your system by changing the clock crystal)
-
- There is a reason why manufacturers don't run the machines at this speed,
- and that is that the hardware simply isn't meant to run at that speed.
- It's not just a case of "Hmm, it runs at 40MHz instead of 33, OK let's call
- it a '40 instead of '33" - the system may run fine at that speed for a while,
- but it's being pushed beyond the manufacturers ratings. There is a reason
- for these ratings - you may be increasing the thermal stress on sections of
- the chip, for example, thus lowering the chip life (this was a major problem
- for Intel when they designed the 66MHz Pentium(c)(tm)(r) - it worked fine at
- lower speeds but localised thermal stress at 66Mhz would fry the silicon).
- Be very careful when you increase the speed like this....
-
- BTW the way many n-MHz CPU's are made is that the manufacturer builds a whole
- batch of, say, 66MHz CPU's. The ones which fail at 66MHz are tested at 50
- and sold as such if possible, otherwise they're tested at 33, then at 25, and
- if they fail that they're encased in plastic and presented to employees as a
- memento. So by running your n-MHz system at n+m MHz you're running it in a
- state which the manufacturer has implicitly branded as being unstable....
-
- Peter.
-
-
-