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Archive-name: acorn/faq/part1 Frequency: bi-weekly Comp.Sys.Acorn FAQ List. ========================= Last alterations 27/Aug/1995 ---------------------------------------------------------------------------- Recent alterations :- * Question 7.5 updated. * Question 7.2 updated. * Question 6.2 updated with a German distributor for !Killer. * Question 4.5 added on the *Speaker command. * Question 5.5 tidied up. * Question 8.3 adjusted to become better HTML. * HTML to Text filter adjusted to cope with & directives as per HTML 2.0 spec. ---------------------------------------------------------------------------- Contained below is a list of the most commonly asked questions about Acorn machines in the comp.sys.acorn heirachy. Before posting to comp.sys.acorn.*, if you are new to the groups, check to see if your question(s) are already answered below. Corrections and/or additions to the list can be emailed to :- banks_p@kosmos.wcc.govt.nz And I'll try to add them as soon as possible.... This FAQ is posted bi-weekly to comp.sys.acorn.misc, comp.sys.acorn.announce, comp.answers and news.answers. The posted sections of the FAQ is available from an email server at MIT. To request the FAQ from this server send an email to mail-server@rtfm.mit.edu . No subject is needed and the body should be :- send /pub/usenet/news.answers/acorn/faq Also the FAQ itself and sub-sections of it are stored in an email server I personally run. See question 7.4 for further details on how to access this email server. For Web browsers out there, the FAQ is available at :- http://www.central.co.nz/~philip/Archives/FaqHTML.html This, like the email server, contains the latest version of the FAQ, as well as a few other documents I have placed up for perusal. Lastly this list is copyright to Philip R. Banks but permission is granted for free distribution of the entire list or quoted segments of it. If you wish to include segments of the list into other documents then proper attribution must be performed and if you wish to include a part of the list, or the list in full, in any commercial product then express permission must be obtained from myself. Index of Questions. The questions have been catagorised loosely into related sections, in an effort to make finding the desired information simpler and quicker. Section 1: Acorn Hardware and Operating Systems. 1.1) What is an Acorn machine? 1.2) What kind of Acorn machines are there? 1.3) What versions of the ARM processors are there? 1.4) What are the main new features of RISC OS 3? 1.5) What are the differences between RISC OS 3.5 and RISC OS 3.11 & 3.10? 1.6) What are the graphics capabilities of the Acorn machines? 1.7) Is Virtual Memory possible under RISC OS? 1.8) What is the current status of Linux for Acorn machines? 1.9) What are the differences between RISC OS 3.6 and RISC OS 3.5? 1.10) What 'Easter Eggs' are present in RISC OS? Section 2: Upgrades and Expansion. 2.1) What are the memory limits of the various Acorn machines? 2.2) What is a second processor and what second processors are there? 2.3) Can PC VGA & Multisync Monitors be added to an Acorn machine? 2.4) Are there any Acorn cards for IBM PC or compatible machines? 2.5) What is a VIDC enhancer? Will I need one for my new multisync monitor? 2.6) What configuration of serial cable should I use for modem work? 2.7) How can I get unfiltered sound from an Acorn machine? 2.8) Can I connect a SCART monitor to my Acorn machine? 2.9) What IDE drives work on Acorn machines? Section 3: Configuration. 3.1) What is ADFSBuffers and what is the best setting for it? 3.2) How do I enable solid drags in RISC OS 3? Section 4: Hardware problems. 4.1) What do the hard drive error numbers mean? 4.2) What can I do with a 'Broken Directory' or a corrupt Free Space Map? 4.3) What does the power on self-test check? 4.4) My Real Time Clock has paused, how do I restart it? 4.5) Why doesn't *Speaker work on my machine? Section 5: Software Issues. 5.1) Why does DOSFS corrupt my files occasionally? 5.2) Where can I obtain the latest version of module X? 5.3) What are the current File-type allocation ranges? 5.4) Is there a Modula 2 compiler for the Arc? 5.5) What Public Domain Languages are available for Acorn machines? 5.6) Why does the RO3.5 desktop sometimes revert to the system font? Section 6: Viruses. 6.1) How can I protect against viruses? 6.2) Where can I obtain !Killer? 6.3) Where can I obtain !SmartKill!? Section 7: Net resources. 7.1) What archives/FTP sites are available? 7.2) What Acorn related companies are available on the net via email? 7.3) Why are comp.{binaries,sources}.acorn empty? 7.4) How to retreive the FAQ from the source... 7.5) What WWW pages are out there for Acorn topics? Section 8: Compatibility with other Machines. 8.1) How compatible with other systems is an Acorn machine? 8.2) Is there a BBC BASIC for other machines? 8.3) Can I run the BBC Emulator on the Risc PC? 8.4) Can I read BBC B formated discs on a PC? Section 9: Technical Details. 9.1) How do I get a faster interupt timer than the centisecond ones? 9.2) How can I create Interlaced GIFs on Acorn machines? ---------------------------------------------------------------------------- Section 1: Acorn Hardware and Operating Systems ---------------------------------------------------------------------------- 1.1) What is an Acorn machine? Acorn computers are a British built line of computers that started with 6502 based machines and now are based on ARM processors. Oddly enough Acorn computers are made by Acorn Computers ( see http://www.acorn.co.uk/ for more details.) Section 1.2 details those machines currently in manufacture and how to fetch a full list of all machines known to have been made by Acorn. Acorn machines are known for their innovation, flexibility and reliability of hardware/software. Reading through section 1 should give newcomers to the Acorn scene a reasonable appreciation of what the machines can do by default. They are fairly strong in education and it is Acorn's primary market. ---------------------------------------------------------------------------- 1.2) What kind of Acorn machines are there? The full list of Acorn made machines is somewhat lengthy now and are mostly no longer in manufacture. Accordingly this list distributed in the FAQ includes only Archimedes/ARM based machines, which are those currently manufactured by Acorn. A full list is maintained in my email server under the filename 'MachineLst'. (see question 7.4 for how to use my email server.) This is, as far as I am aware, a complete list of all Acorn machines made with the possible exception of the latest machines for which I have yet to get the detailed specifications. * A4 - Acorns first portable machine. The A4 is functionally an A5000 in portable form. Featuring power save modes, an LCD screen and software configuration of the power saving features it was released July 1992. It is called the A4 because it's footprint on a desk is apparently that of an A4 piece of paper. It is interesting to note that the A4 is not an A5000 squeezed into portable form but rather the A5000 is the A4 in desktop form, whereby the A5000 design was largely a spin off from the design of the A4. 2048k Memory Advanced Disc Filing System by default with High Density drives. ARM 3 processor. (24 MHz normally, 6 MHz in power save mode.) 12 MHz RAM. (3 MHz in power save mode.) 2048k OS in ROM. ~13.25 MIPS. * A30x0 - Two models of this machine exist the A3010 and the A3020. Both are designed as low end 'family solution' machines. They are also among the first machines to feature the ARM250 processor offering improved performance over an ARM2 (but less than an ARM3) and are designed to supplement the A3000 machine as a low cost entry machine into the Acorn world. Its other main claim to fame is it is the first Archimedes series machine that features joystick ports (only in 3010 model, the 3020 has a network connector instead.). Launched August 27th 1992. 1024k Memory Advanced Disc Filing System by default with High Density drives. IDE 60 Mb Hard Drive (only in A3020 with HD option). ARM 250 processor 12 MHz RAM. 2048k OS in ROM. ~7.2 MIPS * A4000 - This is a higher end more expandable version of the 30x0 series machines and is in a three box format similar to the A5000. It also is driven by an ARM 250 processor however it features over the A30x0 machines optional Ethernet & Econet ports, a high density floppy drive and an 80Mb IDE drive by default. The aim of this machine is strongly towards the home office and more 'serious' applications than the A300x0 series. Launched August 27th 1992. 2048k Memory Advanced Disc Filing System by default with High Density drives. IDE 80 Mb Hard Drive by default. ARM 250 processor 12 MHz RAM. 2048k OS in ROM. ~7.2 MIPS Acorn RiscPC series This is the next generation and architecture of machines - superceeding, but compatible with, the Archimedes range of machines. All of them feature a highly configurable and modular system that makes a bewildering variety of options available. All are founded on the 'second generation' chipset featuring VIDC20, IOMD and the newer ARM6, and better, cell processors. This new range was launched on the 15th of April 1994 with the RiscPC 600 series of machines. The new machines feature the processor card option, the concept of which was first shown in the A540 as well as a unique second processor slot allowing the machines to have two processors in the system, at once, of radically different types. Simply by slipping a 486 chip in, on an appropriate board of course, Intel based software can be run on the machine adjacent to native ARM programs. Both processors share the system resources and can be allocated memory and the like to use. Memory managment has been improved with memory paging always being done in 4K pages. Further more the podule interface has been extended with DMA to and from podules, extended addressing, 32bit data pathways from the IO system as well as a vastly expanded memory map for each podule. Realtime video from the IO system becomes a reality with high speed and data tranfer applications being boosted considerably. These machines are to be the ones to carry Acorn for the next three to six years and look set to do so nicely. * Risc PC 600 series The initial set of machines that launched the RiscPC range. Initially they all featured 30 MHz processors, but as of the Launch of the Risc PC 700 the 600 series machines all feature a 33 MHz ARM 610 instead. RiscPC 600 2M HD210 2048Kb Memory. (No VRAM) Advanced Disc Filing System by default with a High Density drive. IDE interface by default. (210 Mb.) ARM 610 processor (33 MHz) 16 MHz RAM. 2048k OS in ROM. ~26 MIPS. (Arbitrary estimate.) RiscPC 600 5M HD210 4096Kb Memory. (1Mb of VRAM) Advanced Disc Filing System by default with a High Density drive. IDE interface by default. (210 Mb.) ARM 610 processor (33 MHz) 16 MHz RAM. 2048k OS in ROM. ~26 MIPS. (Arbitrary estimate.) RiscPC 600 9M HD420 8192Kb Memory. (1Mb of VRAM) Advanced Disc Filing System by default with a High Density drive. IDE interface by default. (420 Mb.) ARM 610 processor (33 MHz) 16 MHz RAM. 2048k OS in ROM. ~26 MIPS. (Arbitrary estimate.) * A7000 - a successor to the A4000 machine, this is a 'cut down' Risc PC intended for school/home entry as a cheaper alternative to the RiscPC. Both this and the RiscPC 700 are the first machines to feature RISC OS 3.6. Unlike the RiscPC the A7000 has no second processor slot, only one DRAM socket and no VRAM capabilities. This limits the memory expansion of the machine to 128Mb + whatever memory is soldered on the motherboard. Launched 12th of July 1995 A7000 Net 2048Kb Memory. Advanced Disc Filing System by default with a High Density drive. Ethernet interface in place of hard drive. ARM7500 processor. (32 MHz) 16 MHz RAM. 4096k OS in ROM. ~25 MIPS. (Arbitrary estimate.) 2048Kb Memory. Advanced Disc Filing System by default with a High Density drive. IDE interface by default. (425 Mb.) ARM7500 processor. (32 MHz) 16 MHz RAM. 4096k OS in ROM. ~25 MIPS. (Arbitrary estimate.) 4096Kb Memory. Advanced Disc Filing System by default with a High Density drive. IDE interface by default. (425 Mb.) ARM7500 processor. (32 MHz) 16 MHz RAM. 4096k OS in ROM. ~25 MIPS. (Arbitrary estimate.) * Risc PC 700 series is the second generation of Risc PCs to be shipped. They feature the newer ARM710 processor, 16 bit sound as default with audio mixer on the motherboard and RISC OS 3.6. Not so much a major advancement as an incremental improvement of the RiscPC to keep pace with the computing world. Launched 12th of July 1995. RiscPC 700 4M HD425 4096Kb Advanced Disc Filing System by default with a High Density drive. IDE interface by default. (425 Mb.) ARM710 processor. (40 MHz) 16 MHz RAM. 4096k OS in ROM. ~32 MIPS. (Arbitrary estimate.) RiscPC 700 9M HD425 4096Kb (1 Mb of VRAM) Advanced Disc Filing System by default with a High Density drive. IDE interface by default. (425 Mb.) ARM710 processor. (40 MHz) 16 MHz RAM. 4096k OS in ROM. ~32 MIPS. (Arbitrary estimate.) RiscPC 700 10M HD850 8192Kb (2 Mb of VRAM) Advanced Disc Filing System by default with a High Density drive. IDE interface by default. (850 Mb.) ARM710 processor. (40 MHz) 16 MHz RAM. 4096k OS in ROM. ~32 MIPS. (Arbitrary estimate.) ---------------------------------------------------------------------------- 1.3) What versions of the ARM processor are there? The details of all current ARM chips and their capabilities are contained within a file stored in my email server, the filename is 'ARMChips'. See question 7.4 for how to request this file. ---------------------------------------------------------------------------- 1.4) What are the main new features of RISC OS 3? This information is now contained in my email server. If you wish to know the 'new' features of RO3 over RO2 then send a request to my email server, as detailed at the start of the FAQ, for the filename 'RO3diffs'. ---------------------------------------------------------------------------- 1.5) What are the differences between RISC OS 3.5 and RISC OS 3.11 & 3.10? There are alot of behind the scenes differences but the most obvious changes are :- * The system font has been replaced by an outline font. * The Filer uses solid drag icons, including a 'package' icon for multiple file drags. * Error dialogue boxes can now have a button for requesting interactive help on the error. * Windows can have textured backgrounds by default. (This feature can be used independantly of the application supporting it.) * Applications can have up to 28Mb of memory apiece, if available. * The Palette utility has been replaced by the Display Manager, offering an alternative method of choosing screen modes from the older mode number method. * The Task Manager allocates memory via logarithmicly scaled slider bars. * Rogue tasks can be stopped, or killed, by pressing Alt-Break. * The CMOS & hard drive can be protected from alteration. Also, due to the new hardware, there are alot of behind the scenes extensions to the OS including the provision of new dynamic areas, extended podule support, hard drive locking and a wealth of other features. ---------------------------------------------------------------------------- 1.6) What are the graphics capabilities of the Acorn machines? All the Acorn machines are highly upgradable so that they can achieve colour depths and resolutions beyond what is listed here. What is listed here is the default capabilities of the machines as supplied by Acorn. As such it should be taken as a guide to the minimum abilities of the hardware. * 8 bit machines. This covers the BBC Model B, BBC Model B+, Master 128 and ABC range of machines. The display hardware was based on the 6845CRTC chip and was highly flexible for it's time. Resolutions possible :- X res. Y res. Colours 640 256 2 320 256 2,4 160 256 4,16 As well a Teletext character graphics mode and two text only modes were provided by default. The palette range was 16 colours with modes using less than 16 colours capable choosing any mix of the 16 colours, up to the number displayable of course, for display. * 8 MHz ARM based machines. This is the original Archimedes range of machines and covers the A300 series, A400 series, R140 and A3000 machines. The increased capability of the VIDC1a chip dramatically enhanced the resolutions and colours depths possible, namely :- X res. Y res. Colours 160 256 4,16,256 320 256 2,4,16,256 640 250 4,16 640 256 2,4,16,256 640 480 2,4,16,256 640 512 2,4,16,256 1056 250 16 1056 256 16,256 1152 896 2 As can be seen this quite a wide variety of default screen modes. Most are provided to allow driving the various kinds of monitors out there easier, since they are suited to that monitor. The palette range was 4096 colours (12 bit) but the VIDC1a only had 16 hardware palette registers. This meant that in screen modes with sixteen colours or less then the colours could be mapped to any of the 4096 available. However in 256 colour modes 4bits of the colour data are hardware derived and cannot be adjusted. The net result was in a 256 colour a block of 16 colours could be assigned as desired with that block of 16 covering a range of the 4096 available colours. * 12 MHz ARM based machines. This covers the A3010, A3020, A4000, A4, A500, A540 & R260 machines. Here the VIDC1a was still used but it had an extra oscillators added and the primary oscillator was faster (32 MHz) giving finer pixel resolutions. The extra oscillator provided true PC VGA style compatibility for monitors instead of a 24 MHz 'faked' version which sometimes caused problems with intolerant VGA monitors. X res. Y res. Colours 160 256 4,16,256 320 256 2,4,16,256 640 200 2,4,16,256 640 250 16 640 256 2,4,16,256 640 352 2,4,16,256 640 480 2,4,16,256 640 512 2,4,16,256 768 288 2,4,16,256 800 600 2,4,16 896 352 2,4,16,256 1056 250 16 1056 256 16,256 1152 896 2 Because the display hardware was essentially the same as the 8MHz machines' the palette handling was identical. * Risc PC machines. This covers all Risc PC in the Risc PC 600, Risc PC 700 & A7000 machines. Here the newer VIDC20 chip has been used and the display capabilities are somewhat extended. Namely :- X res. Y res. Colours 160 256 4,16,256 320 256 2,4,16,256 640 200 2,4,16,256 640 250 4,16 640 256 2,4,16,256 640 352 2,4,16,256 640 480 2,4,16,256 640 512 2,4,16,256 768 288 2,4,16,256 800 600 2,4,16,256,32k*,16M** 896 352 2,4,16,256 1024 768 16,256*,32k** 1056 250 16 1056 256 16,256 1152 896 2 1280 1024 4,16*,256** 1600 1200 16*,256** * Requires 1 MB of VRAM ** Requires 2 MB of VRAM With the addition of Video RAM (VRAM) to the Risc PC the base capabilities are a touch variable, thus the note next to some of entries. All other modes are available with standard DRAM, and these the only modes the A7000 can access. Furthermore the new VIDC20 has 256 palette registers, compared to the VIDC1a's 16, and a palette range of 16 million colours. Exactly how the colour mapping in 32,000 modes is handled is not yet clear. Again these are just standard screen modes provided, and even perhaps not all of them - the Risc PC is completely configurable in display resolutions and capabilities. It must be stressed again that these are merely the resolutions and colour depths defined by the machines operating systems. In all of the machines cases there are both hardware and software extensions that alter and increase the list. ---------------------------------------------------------------------------- 1.7) Is Virtual Memory possible under RISC OS? Short answer, full VM is not possible under the current versions of RISC OS. The problem is that most of RISC OS works in SVC mode, if a DataFetch abort occurs then R14_svc is corrupted . This makes returning from the SWI somewhat problematic. This is a hardware limitation with the ARM2 and ARM3 cell chips. Future hardware using ARM6 or better processor cells have special memory abort modes that alleviate this problem so future machines and incarnations of RISC OS may well have VM available. Indeed the new RiscPC machines make prime candidates for having virtual memory, however there are still re-entrancy issues that make this problematic for RISC OS. (Consider loading data from a file into paged out virtual memory...) However limited solutions are available now. !Virtual is one such solution allowing VM for a user process using a limited subset of SWI's that are carefully 'protected' against R14_svc being corrupted. Such solutions suffer from the restricted set of SWI's they support and are mostly useful for batch style processing jobs like compilation or memory intensive processing jobs. !Virtual currently does not work with Risc PCs due to the fact that it requires a page size which is a multiple of 8kb. (This means !Virtual will not work with A305s.) ---------------------------------------------------------------------------- 1.8) What is the current status of Linux for Acorn machines? Due to the rapid development of Linux exact details about the latest incarnation of Linux are not kept in this FAQ. However for the latest information you might like to consult these web pages, or email the people involved with the port :- Native Linux page :- http://whirligig.ecs.soton.ac.uk/~rmk92/armlinux.html (rmk92@ecs.soton.ac.uk) PC card Linux :- http://www.ph.kcl.ac.uk/~amb/linux.html (amb@physig1.ph.kcl.ac.uk) ---------------------------------------------------------------------------- 1.9) What are the differences between RISC OS 3.6 and RISC OS 3.5? Quite a few, although nothing particularly drastic OS wise, mostly improvments although the lifting of the FileCore partition limit and the incorporation of JPEG handling into the OS are quite substantial improvements. Here is the list :- * Now stored on 2x2Mb ROMs, or an increase ot a potential 4096Kb of OS. * FileCore improvements allowing at least 4Gb partitions. * Support for ATAPI style CD-ROM drives. * JFIF handling incorporated into the OS. * Standard applications have been moved back into ROM. * Toolbox modules, the Cv5 support modules, moved into ROM. * CDFS modules moved into ROM. * Access modules moved into ROM. ---------------------------------------------------------------------------- 1.10) What 'Easter Eggs' are present in RISC OS? It has been a long tradition with Acorn OSes to have hidden sections that give credit to the people involved in the creation of that OS. The BBC Model B ROMs had the names of the people involved hidden in the memory space occupied by Fred, Jim and Shelia. With the release of the ARM powered machines this tradition has continued on. * RISC OS 2.00 * tucked away in the ROMs is a list of the names of involved people. * RISC OS 3.00 * If you type 'rmtmd' when the desktop welcome screen is displayed a slide show of the key RISC OS team members is displayed on the screen. * In the info box of the task manager if you clicked menu over the letters 'rmtmd', in that order, contained within the author icon a full list of the people involved with the OS's development is displayed in that icon. * RISC OS 3.10 & 3.11 * In the info box of the task manager if you clicked menu over the letters 'team', in that order, contained within the author icon a full list of the people involved with the OS's development is displayed in that icon. * Using a template editor examine the task managers templates file from the Resources filing system. (Resources:$.Resources.Switcher.Templates) Inside the 'power' dialogue is a message. * RISC OS 3.50 * In the info box of the task manager if you clicked menu over the author icon four times a full list of the people involved with the OS's development is displayed in that icon. (This can take a while to watch, be warned...) * Using a template editor examine the task managers templates file from the Resources filing system. (Resources:$.Resources.Switcher.Template3D) Inside the 'power' dialogue is a message, in 3D. This message also appeared in the replacement templates supplied with NewLook for RISC OS 3.1. ---------------------------------------------------------------------------- Section 2: Upgrades and Expansion. ---------------------------------------------------------------------------- 2.1) What are the memory limits of the various Acorn machines? For the most part the 8 bit machines were limited to a maximum of around 256k of memory. Although various expansion systems including second processors effectively meant the upper limit was about 1 Meg. (Although I have been told of a second processor with 4 Meg of memory in it. ) For the early 32 bit machines the upper limit currently is 16 Meg of memory. Not all of the range of machines are capable of this however and the list looks something like this :- A3xx - 8 Mb maximum through third party, 1 Mb official limit. A4xx - 8 Mb maximum through third party, 4 Mb official limit. A4xx/I - 8 Mb maximum through third party, 4 Mb official limit. A3000 - 8 Mb maximum through third party, 2 Mb official limit. A540 - 16 Mb maximum. A5000 - 8 Mb maximum through third party, 4 Mb official limit. A4 - 4 Mb official limit. A30x0 - 4 Mb official limit. A4000 - 4 Mb official limit. A5000 - 8 Mb official limit. (alpha variant of the A5000) A7000 - 128 Mb + memory on mother board. (Tops out at 132 Mb and requires a 128 Mb SIMM to do it.) Newer RiscPC machines have an official upper limit of 256 Mb, plus 2 Mb of VRAM, on all models. However this does require you using 128 Mb SIMMS which are currently not very common... ---------------------------------------------------------------------------- 2.2) What is a second processor and what second processors are there? A second processor was the generic name for a range of parasite processors that could be linked to Acorn's 8 bit machines via what was called the `Tube` interface. Basically the host machine became dedicated to handling the Input and Output while the second processor would do the higher level functions (like running your programs). The second processor ran asyncronously to the host processor allowing incredible increases in execution speed for programs. A wide range of processors were supported this way allowing Acorn's eight bit range of machines to remain viable and useful for much longer than their technology would suggest. The Second Processors that existed are :- * Z80 second processor. 6 MHz RAM. 64k Memory. CP/M OS. External second processor for all eight bit machines. * 6502 second processor. 3 MHz RAM. 64k Memory. Extended version of the BBC MOS. External processor for all eight bit machines. * 32016 second processor. 6 MHz RAM. 256k-4096k Memory. Panos. External processor for all eight bit machines. * ARM 1 second processor. 4 MHz RAM. (At a guess...) 4096k Memory. Brazil OS. External processor for all eight bit machines. * 6502 co-processor. (internal second processor). 4 MHz RAM. 64k Memory. Extended version of BBC MOS. Internal processor for Master 128 machines but could be fitted external to the other eight bit machines. * 80186 co-processor. 10 MHz RAM. 512k Memory. DR-DOS+ with GEM. Internal processor for Master 128 machines but could be fitted external to the other eight bit machines. ---------------------------------------------------------------------------- 2.3) Can PC VGA & Multisync Monitors be added to an Acorn machine? It depends on what monitor you have, and what Acorn machine you have. There are two main types of PC VGA monitors out there... * Fixed Frequency These monitors will only display video signals with certain line and refresh rates. They will typically only display CGA / EGA / VGA modes. * Multi Frequency These monitors will display any video signal within a certain range, typically 30-50Khz line rate and 50-80Hz refresh rate. Type 1 almost always require separate syncs as the monitor uses the polarity of the syncs (mainly positive going negative or mainly negative going positive) to determine what the line and refresh rate should be. Type 2 vary. Some require seperate syncs (vertical and horizontal) and others will work with composite syncs (vertical and horizontal EOR together). As PC monitors typically start at a line rate of 30Khz compared to the TV broadcast modes (mode 12 etc.) that have a line rate of 15Khz, VIDC has to do more work to obtain a 30Khz line rate. This means that you computer will slow down silghtly if you use a 30Khz+ line rate monitor. If you have an ARM 3 fitted such slow downs will probably be negligible. Now, depending on what type of Archimedes you have depends on what type of monitor you can use. * A540 / A5000 / A4 / A3010 / A3020 /A4000 Has software control over the polarity of the syncs and what frequency VIDC is clocked at. The A540 with RISC OS 2 can only use modes 26-28 (640x480) and 31 (800x600). However, by changing links and a *configure option, you can get the computer to generate seperate syncs with no problem. The other machines with RISC OS 3 can do even better. If you tell the computer that you have a VGA monitor it will re-map all of the 15Khz line rate modes up to 30KHz line rate. This means that you can play your games that require mode 12 / 13. However, as a PC monitor is designed to display 320 lines minimum then you will get a 'letterbox' effect as mode 12 has only 256 lines. All these machines have 24Mhz, 25.175Mhz and 36Mhz crystals to drive VIDC with. The 25.175Mhz crystal is needed to obtain the correct video rates for PC monitors displaying 640x480 screens. The 36Mhz crystal is used to obtain higher resolution modes, like 800x600x16 colours. * A3000 This can generate seperate syncs but requires links to be set to determine the polarity. It has only a 24Mhz crystal and can therefore only drive 'forgiving' monitors correctly that don't mind the 640x480 video mode timings being slightly incorrect. The links to change, to set the sync polarity, are as follows: Link 24: Change from SOUTH to NORTH Link 25: Change from OPEN to CLOSED In order to obtain proper timings, and software control of the sync polarity, you will need a VGA VIDC Enhancer for the A3000. * A400 series. The situation gets more complex. Due to an 'error' in the PCB / circuit diagram, the A400 series cannot generate seperate syncs satisfactorily. The video signal loses the green component when seperate syncs is selected. It has been reported to me that 400/I series machines may have this fault corrected and not lose the green component. As standard, there is no polarity control over the syncs. In common with the A3000, there is only a 24Mhz crystal. Also it is links 1 and 2 that need changing. If the PC monitor can handle composite syncs then the monitor can be used in 640x480 mode only. * A300 series. Most, if not all, of the A300 series had the circuit board hardwired into composite mode continuously. There is only a 24Mhz crystal, and only composite sync monitors can be used. Also the A300 suffers the same problem as the A400, it looses green component in seperate sync mode. * RiscPC series. This has a very flexible VIDC in it and is quite capable of driving PC monitors with no trouble. However to connect an older machine (A3000,A300,400 series) to a VGA monitor, you will need a means of connecting the standard 15-pin VGA plug to the 9-pin socket in the computer. A number of companies sell 'converters', but all this boils down to is a lead with the following configuration :- .------------------------. VGA 15-pin socket \ 1 2 3 4 5 / \ 6 7 8 9 10 / \ 11 12 13 14 15 / '------------------' .------------------------. Arc 9-pin plug \ 1 2 3 4 5 / \ / \ 6 7 8 9 / '------------------' Signal VGA pin Arc pin Gnd 10 9 Red 1 1 Green 2 2 Blue 3 3 R gnd 6 6 G gnd 7 7 B gnd 8 8 H 13 4 V 14 5 In conclusion, apart from the A5000 and newer machines, no computer as standard can drive either a fixed frequency or multi-frequency PC monitor in all of the Archimedes modes satisfactorily. However VIDC enhancer boards can be bought to upgrade an Archimedes series machine to handle the needed timing and signals. ---------------------------------------------------------------------------- 2.4) Are there any Acorn cards for IBM PC or compatible machines? Yes. Three cards in total :- * Springboard. ARM 2 processor. 4096k Memory. 8 MHz RAM. Brazil OS. * PC ARM development system. Precursor to Springboard. Hardware functionally identical. * Ecolink. An econet link card for the PC. ---------------------------------------------------------------------------- 2.5) What is a VIDC enhancer? Will I need one for my new multisync monitor? A VIDC enhancer is basically a clock change for your VIDC. Most Arcs (bar the A540 and newer machines) have 24 MHz VIDC chips installed in them. A VIDC enhancer increases this to 36 MHz allowing much higher resolution screen modes to be displayed on your Arc. (800x600x16 or SVGA standard becomes available.) You do not need one to use a Multisync monitor - the standard VIDC handles that just fine. However having a VIDC enhancer is only really useful if you do have a Multi-sync monitor. Note a VIDC enhancer is unneccesary and incompatible with the RiscPC range of machines. ---------------------------------------------------------------------------- 2.6) What configuration of serial cable should I use for modem work? Here follows a diagram of the necessary connections for common terminal programs to work properly. They are as far as I know the informal standard agreed upon by commercial comms software developers for the Arc. Pins 1, 4, and 8 must be connected together inside the 9 pin plug. This is to avoid the well known serial port chip bugs. The modem's DCD (Data Carrier Detect) signal has been rerouted to the Arc's RI (Ring Indicator) most modems broadcast a software RING signal anyway, and even then it's not really necessary to detect it for the modem to answer the call. Arc (9 pin) Modem (25 pin) ----------- -------------- +---1---DCD | | 2---RxD------------------------RxD----3 | | 3---TxD------------------------TxD----2 | +---4---DTR------------------------DTR---20 | | 5---0v-------------------------SG-----7 | | 6---DSR------------------------CTS----5 | | 7---RTS------------------------RTS----4 | +---8---CTS 9---RI-------------------------DCD----8 Of course you can connect the Modem pin 20 to any one of pins 1, 4, or 8 on the Archimedes plug, as they are all connected together anyway. Chocks Away Extra Missions (the flight simulator from 4th Dimension) suggests that the serial cable be wired as above except that pins 1-4-6 are connected together and the modem's CTS (pin 5) be connected to the Arc's pin 8 (ie the connections at pins 6 and 8 be swapped over at the Arc's end). This has been and it also seems to work fine. However newer Arc's like the A5000 have come out (and indeed the occasional A310) with a `corrected` serial port. This newer serial port operates as it should and is directly compatible with standard PC cables. Most comms software about at the moment does not take this in account and assumes that you have a cable patched in the manner described above. If you do not use such a patched cable on these `fixed` serial ports the software will generally fail to work completely. With the advent of the Risc PC a standard PC cable is advised. ---------------------------------------------------------------------------- 2.7) How can I get unfiltered sound from an Acorn machine? All Acorn machines are equipped with a sound filter designed to remove high frequency harmonics from the sound output. However this does cause a muffled feel to the sound as on some machines the filter is a little too excessive and it filters out valid frequencies. Also the filter is optimised for 20.833 kHz output and has less desirable results when the output rate is changed. Accordingly people who do audio work often want to bypass the filter. On all machines bar the A3000 there is the Internal Auxiliary Audio Connector (usually called link LK3), which can be easily plugged into to provide the unfiltered output. This connector has 10 pins on it and is usually found near the headphone socket on the motherboard. The pins are :- 1 Unfiltered Left 2 Ground 3 Filtered Left 4 Ground 5 Auxiliary Input 6 Ground 7 Filtered Right 8 Ground 9 Unfiltered Right 10 Ground Simply hook into the Unfiltered outputs. On an A3000 you need two 10uF 16V ALEC capacitors. Look for chip LM324 (IC39) and hook the capacitors like this :- Pin 1 --> --|+ |--- Unfiltered Left Pin 2 --> --|+ |--- Unfiltered Right The Risc PC & A400 machines have a connector similar to the A5000. There are several caveats to this procedure. Opening your machine may void your warranty and most definitely should not be attempted if you are unsure of the procedure. Do not unplug/plug the unfiltered audio output while the machine is turned on, by bypassing the filter you also bypass the normal protective circutry for the audio output. Finally you will hear higher harmonics present in the audio signal so you will need to connect the signal to a filter of some kind to reduce this extra noise. ---------------------------------------------------------------------------- 2.8) Can I connect a SCART monitor to my Acorn machine? If you have an older Acorn machine with a nine pin video socket, then yes and here is the wiring diagram :- .------------------------. Arc 9-pin plug \ 1 2 3 4 5 / \ / \ 6 7 8 9 / Case '------------------' _____________________ |19 1| SCART 21-pin plug | | | | | | | | | | | | / | / | | | | | | | | | | | /___20_________________2_| 21 (metal casing) A SCART connector is also known as a Euroconnector or a Peri-Television connector. Arc SCART Case | ------------- 21 Case Red 1 ------------- 15 Red Green 2 ------------- 11 Green Blue 3 ------------- 7 Blue CSYNC 4 ------------- 20 Composite video input Ground (0V) 6 -+---------+- 13 Red ground Ground (0V) 7 -+ +- 9 Green ground Ground (0V) 8 -+ +- 5 Blue ground Ground (0V) 9 -+ +- 13 CVBS video ground Ideally each ground wire should be linked to a separate Arc pin. Also, depending on your SCART monitor, pin 16 may need a +5V input to it. Unfortunately the Arc 9 pin socket does not provide a +5V output so this will have to be sourced from somewhere else. If you have a newer Acorn machine, with the 15 pin high density video socket then you need this kind of wiring :- .--------------------. 15-pin VGA style plug \ 1 2 3 4 5 / \ 6 7 8 9 10 / \ 11 12 13 14 15 / '--------------' Connections: Arc SCART 1 red ---------------------------- 15 2 green--------------------------- 11 3 blue---------------------------- 7 4 ID[2] nc 5 0V (test) 6 red rtn------------------------- 13 7 green rtn----------------------- 9 8 blue rtn------------------------ 5 75 ohms 9 +5V-------------/\/\/\/--------- 16 10 0V----------------------------- 17,18 12 ID[1]-------------------------- 8 11 ID[0] 11 | 120 ohms 14 CSync------------/\/\/\/------- 20 15 ID[3] nc Notice the two resistors. Also notice that the HSync output (pin 13) of the 15-way plug has to be connected to the ID[0] input (pin 11) of the same plug. (Be aware I have no direct confirmation that this wiring works .) As is usual care must be taken when doing this procedure. Older Acorn machine did not have their VIDC chips fully buffered and unplugging/plugging cables from the video socket while the machine is turned on can cause damage to the video circutry. ----------------------------------------------------------------------------