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*** CP/M-COMPATIBLE COMPUTING ALIVE AND HEALTHY IN 1988!! ***
<This is a compilation of recent messages appearing on Z-Node
Central pertaining to the Z280 chip. It has been compiled
entirely by Dreas Nielson, and edited slightly by Rick Charnes
1/1/88. Some real nice and informative discussion here -- our
CP/M-compatible world is still moving forward very nicely.
Thanks to Dreas Nielsen for capturing these messages from ZNC.
He originally compiled them into three files; I put them into one>
P.S. -- For us Morrow users I've added a couple of notes from
Scott Moore from Ladera Z-Node in L.A. at the end noting that
he's been able to put in the Zedux DIRECT Z280 board (the
computer is no longer using the Z80 chip at all, not even as a
coprocessor!) into the Morrow MD3 we've lent him! Once again
Morrow is at the top of the pack! All (?) we need to do is
rewrite the Morrow BIOS (remember the 64180 project?) - rc
-------
Message #13005 ** General **
Posted: 11/23/87 at 8:19 am
From: Dave Vanhorn
To: Ron Bardarson [read 01/01/78 at 12:59 am]
About: z-280 (4 lines)
I have a chip. My folks at Zilog tell me to expect the 50Mhz versions
in the next 90 days. I have not found any trap problems as previously
alluded. The traps are only active in user mode and the chip powers
up in system mode. I have a Z-280 to Z-80 plugboard running also.
-------
Message #13028 ** Z-System **
Posted: 12/05/87 at 12:55 pm
From: Ron Bardarson
To: Ben Grey [read 12/07/87 at 6:21 am]
About: Z-280 (12 lines)
Hi Ben, actually I was hoping to keep this Z-280 discussion public.
I'm a very big fan of Z-80's and Zilog and was playing devil's
avocate to stir up the msgs here at ZNC. I have also seen a Z-280
demo organized by Rich Charnes. Unfortunately whoever gave the demo
didn't know a thing about Z-System, they were running their own private
OS. Their Z-280 impletmention wasn't going to allow interrupts or
poking system bytes, as an owner of 3 BigBoard II's ( Mode-2 interrupts)
I wasn't impressed. As a hacker, I would have been handcuffed. They
were also going to trap I/O calls, another poor idea. As for Kaypros,
I don't know what could have failed to follow spec, I have mine running
at 8 MHz without problems, but then I've tinkered with it a bit.
-------
Message #13030 ** Z-System **
Posted: 12/05/87 at 1:07 pm
From: Ben Grey
To: Ron Bardarson [read 12/05/87 at 1:08 pm]
About: Z-280 (17 lines)
Ron: The implementation of the Z280 OS/Z by Zedux is not limited in
the manner you suggest. I suspect it is because you don't understand
what it takes to "simulate" CP/M (ZRDOS or whatever) and in the environment
that they were working in. I've spent many hours working on some of
the problems that one has to deal with to put a Z280 in a Z80 system.
It is not simple! The fact that your demo didn't come off too well,
cuz of the broken boards, should not have been a factor. Scott Moore
is a Unix/VM-370 type and he has implemented all the various functions
we normally have under Z_system in his new OS. The fact that they have
to trap I/O and don't allow poking is all very well and good. But what
you might not realize is that any program which uses self modifying
code will NOT run in a Z280... There simply is no way to address the
bytes in the program (data segments, yes, code segments, no). FYI,
Greg Trice, Toronto, has a working S-100 version and is quite a good
Hardware type. You and he probably ought to chat when you can... Ben.
-------
Message #13032 ** Z-System ** [reply to #13030]
Posted: 12/05/87 at 1:37 pm
From: Ron Bardarson
To: Ben Grey [read 12/07/87 at 6:23 am]
About: Z-280 (20 lines)
If you can't poke system bytes then :
the poke and go techniques are lost!
Zex is lost
Memory Editors are reduced in usefullness
Error handling and message communications are lost!
.... All of these programs and many more use parts of the operating
system to communicate or gain services. They REQUIRE poking system
bytes to work. If the Z-280 doesn't allow this, then it is NOT an
upgrade to Z-System.
If you can't use I/O outside of the operating system then :
Kiss your modem programs goodbye
Forget about BYE and RAS's ( BYE would need to be re-written anyway)
No more special printer drivers
No more custom I/O drivers for controller purposes ( SCSI, etc..
.... Most of these programs don't use the operating system for I/O.
Again if the Z-280 doesn't allow this, then it's a step backwards.
The fact that Scott's demo didn't work had very little to do with my
opinions, they were generated as a direct result of Scott's talk.
-------
Message #13041 ** Z-System ** [reply to #13032]
Posted: 12/07/87 at 6:30 am
From: BEN GREY
To: Ron Bardarson [read 12/07/87 at 7:25 pm]
About: Z-280 (19 lines)
Well Ron, It's apparent you do not understand how the memory management
of the Z280 works. Code segments simply cannot modify themselves. There
is no need for a BYE or RAS or any of the usual selfmodifying programs
in a system that uses the Z280 (at least not the OS/Z). There is nothing
preventing loading of "system" segments that take care of printers
and terminals, hard disks, and so on. The idea that the Z280 can't
do I/O is patently absurd. It can, but in general it cannot run directly
in a Z80 environment. The co-processor can -- but it has the old Z80
to do it's I/O and transfer info into and outof the Z280's memory.
I suggest you contact Zedux on your own and get their literature before
you rail at me for explaining what most every system designer who has
looked at the Z280 already knows. For $10 I'll send you the newest
data book. As soon as I get my 1MB DRAM, I'll but running the Z-node
with a Z80-280 combination. We'll see what I can/can't use. Programs
that worked before will work just as they always did, just the data
areas will be in data memory and not in code memory. There are very
good reasons for not permitting self-modifying code. We surely don't
want lowly CP/M programs crashing our OS...
-------
Message #13045 ** Z-System ** [reply to #13041]
Posted: 12/07/87 at 7:32 pm
From: Ron Bardarson
To: BEN GREY
About: Z-280 (10 lines)
Ben ah take a closer look at my replies, nowhere do I say we can't
use 280's. ALL THAT I HAVE SAID IS THAT THEY WILL NOT BE Z-SYSTEM COMPATIBLE
If you would like to regenerate the code, fine. As for what you'll
be able to run or not, thats the very important test that I'm waiting
for before I invest a penny, since I know that the 280 is not Z-System.
No doubt that it's a better processor, but so are several others.
The only thing that's attractive is if it is almost fully Z-System
compatible, thus allowing all of us to hardware upgrade without
software re-investment. If it takes that ( both hardware and software)
then I'll get a 68030 system.
-------
Message #13053 ** General **
Posted: 12/08/87 at 7:41 pm
From: Dave Vanhorn
To: Ron Bardarson
About: z-280 (20 lines)
FIFTY MEGAHERTZ. 50 CPU clock then = 25 mhz, and system clock is
(on the buss) 12.5 mhz. (Assuming you can dig up some Z-80(Q?) I/o
chips that will go that fast!) Waitstates up the wazoo I think!
Unless some bright person used a Z-80 as an I/O processor and blasted
the I/O information out to the Z-80's ram using the DMA and common
memory areas... (Who would do a thing like that?)
I'm making a shift in my 280 experiments. The CP/M machines that exist
now are too diverse in their hardware for a Z-280 fit-in to be anything
but a cripple, so i'm looking at putting a Z-280 into a PC and using
the 80XXX as an I/O manager. It will be fully Z-System compatible,
running Z-80 code unmodified. The trickiness comes in when the bios
calls are done, and they actually pop the data in and out of the pc's
ram for handling by the 80xxx on the pc iron. I'll probably put a
SCSI port on the 280 board, and might consider a floppy port as well
to make r/w of existing CPM formats easier. The use of the PC iron
gives us CHEAP boxes, and bits,, and should go a long way twoard standardizin
g the software as well. (Maybe the best of both worlds?)
Imagine: One board turns a PC into a real computer! What a concept!
-------
Message #13054 ** General **
Posted: 12/08/87 at 7:46 pm
From: Dave Vanhorn
To: Ron Bardarson
About: z-280 (11 lines)
I forgot to mention: Caching WORKS! I have made measurements on code
executing in rom-based systems that PROVE the cache does work. It's
real spooky to see it suddenly stop doing bus transactions (xcpt for
refresh) when it drops into a tight loop!)
As for CP/M programs not running, well.... My ampro dosen't seem to
notice that it has a Z-280 card plugged into it's Z-80 port... Z-system,
MEX-PC, and all my little wierd programs are running just fine.
It strikes me that someone is piping lots of anti-280 rumours out into
the world. Could it be that the cloneheads are getting nervous?
-------
****
Messages re Z280 captured from Z-Node Central 12/14/87
-------
Message #13069 ** General **
Posted: 12/10/87 at 11:21 pm
From: TONY PARKER
To: DAVE VANHORN [read 12/12/87 at 2:43 pm]
About: Z280 on a Kaypro??? (3 lines)
Dave;
Is there a real live "non-vaporware" ready to buy board or series of
parts That I could get up and running Z on my Kaypro!!!!TP
-------
Message #13078 ** General ** [reply to #13069]
Posted: 12/12/87 at 2:44 pm
From: Dave Vanhorn
To: TONY PARKER
About: Z280 on a Kaypro??? (2 lines)
Only one I know of is the ZeDux machine, and I'm not sure of it's status
as vapor/hard ware. (I've not seen one...)
-------
Message #13082 ** General ** [reply to #13053]
Posted: 12/12/87 at 3:14 pm
From: Ron Bardarson
To: Dave Vanhorn [read 12/14/87 at 12:06 am]
About: z-280 (5 lines)
I'd heard of the idea of using PC chassis as a home for 280's, seems
like a very good idea since the cost of clones is so low and there
are expansion abilities built right in ( along with the cards to fit).
In short, are you looking for a poor soul to test if all that CP/M
software can run on it? I know one or two.....
-------
Message #13101 ** General ** [reply to #13082]
Posted: 12/14/87 at 12:08 am
From: Dave Vanhorn
To: Ron Bardarson [read 12/14/87 at 5:46 pm]
About: z-280 (4 lines)
I checked with Z-world, and they aren't planning to do a board like
this. I put in a message also to Rick over at Ampro, but I rather doubt
they are planning anything. I may be forced to drag out the old wire
wrapping gun again!
-------
Message #13105 ** General ** [reply to #13101]
Posted: 12/14/87 at 5:50 pm
From: Ron Bardarson
To: Dave Vanhorn [read 12/14/87 at 6:31 pm]
About: z-280 (9 lines)
Do you have a reply to Grey's cache statement? Never pay much attention
to people who tell me that it would take too long to explain myself.
Old rule of thumb for physicists, if it doesn't fit on one sheet of
paper and you can't explain it to everybody, then you don't understand
it yourself.
Have you tried your board in any other machines? I may be travelling
down your direction in the next few months, perhaps I could get
a peek?
-------
Message #13106 ** General ** [reply to #13105]
Posted: 12/14/87 at 6:35 pm
From: Dave Vanhorn
To: Ron Bardarson
About: z-280 (6 lines)
I measured the caching by looking at the buss while executing code
which all fits within the 16 byte limit of the cache. I saw caching
take effect when the 280 stopped doing the memory reads required to
fetch the data off the eprom. Apparently in some other cases it acts
differently. Remember, it's not a BIG cache, just 16 bytes. Still,
it's better than nothing.
-------
Message #13083 ** General ** [reply to #13054]
Posted: 12/12/87 at 3:22 pm
From: Ron Bardarson
To: Dave Vanhorn [read 12/14/87 at 12:08 am]
About: z-280 (11 lines)
Well I heard that the cache didn't work from someone trying to sell
Z-280 boards, but rumors are only as reliable as their source. Glad
to hear that your weird programs run, as I have a number myself that
sounded like they wouldn't work. I'm also an amateur radio operator
and have some custom code running my FT-980 transceiver, for which
I need several I/O ports and interrupts. I'm working toward a frequency
agile CW robot one of these days.....
As for anti-280 rumors, I doubt if the cloneheads understand hardware
enough to realize what the excitment is about, glad to hear you have
a running system.
-------
Message #13085 ** General **
Posted: 12/12/87 at 3:41 pm
From: Ron Bardarson
To: TONY PARKER
About: Z280 on a Kaypro? (1 lines)
Check with Ben Grey, you can leave a msg here or on his Z-Node.
-------
Message #13090 ** General **
Posted: 12/13/87 at 10:29 am
From: BEN GREY
To: TONY PARKER
About: Z280 on a Kaypro!!!??? (1 lines)
There is no Z280 for *ANY* Kaypro machines at this time.
-------
Message #13091 ** General **
Posted: 12/13/87 at 10:35 am
From: BEN GREY
To: Ron Bardarson [read 12/13/87 at 8:30 pm]
About: Z280 (10 lines)
I guess the problem with even the Z80 users and those that are not
familiar with the way the hardware works, it is impossible to explain
what the difficulties with the Z280-Z80 situation is. As for running
Z-System on a Z280 is concerned, there is absolutely no problem with
do so. The fact that you don't have a BIOS or BDOS plays absolutely
no role in the scenario whatsoever. It is the function of the OS to
provide the "system functions" we normally associate with the BDOS
and BIOS. If they don't exist, then the problem becomes on of how do
CP/M programs of any sort expect to run on a Z280? The fact is, they
can and do run, without difficulties. \
-------
Message #13092 ** General **
Posted: 12/13/87 at 10:39 am
From: BEN GREY
To: Dave Vanhorn [read 12/14/87 at 12:09 am]
About: Z280 Cache (9 lines)
The Z280 cache problem is NOT fixed!! Unless you have received a chip
in the past two weeks (unlikely) you are still running with the last
batch issued in July. The problem is not easily explained, but it
can be demonstrated with programs that set the stack to the address
below the CCP and programs which gobble memory up to that point. The
cache controller simply gets confused and mixes bit/bytes/words in
such a way it nearly impossible to track. The cache does work in some
cases where the program is *very well behaved*. No word from Zilog
on when the "cache insect" will be removed. I suspect in Jan 88.
-------
Message #13102 ** General ** [reply to #13092]
Posted: 12/14/87 at 12:12 am
From: Dave Vanhorn
To: BEN GREY
About: Z280 Cache (4 lines)
Hmm.. The program I set up to test cacheing is probably a 'very well
behaved' program. I've not monitored the buss with normal programs
running since the TEK 1240 has this problem in not recognizing opcode
fetches without the M1 signal. Have faith.
-------
Message #13094 ** Z-System ** [reply to #13045]
Posted: 12/13/87 at 11:00 am
From: BEN GREY
To: Ron Bardarson [read 12/13/87 at 8:33 pm]
About: Z-280 (25 lines)
I guess i need to iterate again that the difference between Z-System
and Z280 is like the difference between dumplings and road apples.
Hardware does not an operating system make. It is the OS that makes
the computer in the long run and it is the OS function to provide the
user with the necessary hooks to accomplish that which he want to create.
It is too unfortunate that folks like to compare hardware and software
in the same sentence. They are distinctly different.
The problem with putting a Z280 in an existing Z80 machine would not
be nearly so complex if each manufacturer had followed the letter of
the Zilog Z80 specifications and designed for the worst case. The did
not, and played games with the bus timings and various other signal
timings making a "universal" replacement exceedingly difficult. The
classical case is the Kaypro machines.
If you really care to follow along with Z280 info, you should be checking
in on Al Hawley's system from time to time (weekly if you can) as there
is much discussion about it and the "new breed" of OS we are likely
to see in the very near future. I have no problem playing devils advocate
with this issue, since I've got a Z280 here too, and am busy (what
with all my other projects) designing a Z280 system that has a full
potential. The fact that I've unloaded the Z280 from it's mundane chores
and left it for the work it can do best is academic. Who wants to bog
such a machine down with slooow I/O or such? Oh well, such is the life
of a hardware/software engineer.
-------
Z280 Messages captured from Z-Node Central 12/19/87
-------
Message #13109 ** General ** [reply to #13106]
Posted: 12/14/87 at 11:20 pm
From: Ron Bardarson
To: Dave Vanhorn [read 12/16/87 at 10:57 pm]
About: z-280 (3 lines)
Thanks for the info on the cache test, did your wire wrap comment
indicate that you were planning on building more Z-280 boards?
Have you tried it in any machines other than an Ampro?
-------
Message #13135 ** General ** [reply to #13109]
Posted: 12/16/87 at 11:00 pm
From: Dave Vanhorn
To: Ron Bardarson [read 12/17/87 at 1:00 am]
About: z-280 (5 lines)
I've tried it in the ampro, and in several of our Z-80 based credit
card terminals. I am looking at doing a Z-280 in a PC card. (Similar
to the Z-world (Formerly Decmation) blue lightning/thunder cards, but
with Z-system as the main DOS with PC operation as an auxilliary)
Mainly for a fixed environment with cheap hardware.
-------
Message #13146 ** General ** [reply to #13135]
Posted: 12/17/87 at 1:07 am
From: Ron Bardarson
To: Dave Vanhorn
About: z-280 (4 lines)
Hey you could use the extra memory clone buyers get ( 1 Meg) only to
find out they can access 640K....seriously clone chassis make
sense, as I said earlier. Ampro schematic looks like most I've seen,
wonder why other people are having problems.
-------
Message #13114 ** General **
Posted: 12/15/87 at 5:35 pm
From: Frank Gaude'
To: ALL USERS
About: PZDOS (5 lines)
Just a quick note to state that Echelon is actively working out an
arrangement with Cameron Cotrill, et al, to handle PZDOS, the Z80 DOS
we intend to be the DOS that upgrades ZRDOS beyond v1.9. More as the
agreement and product near finalization and release, respectively.
Echelon, Inc.--from high in the Sierras...
-------
Message #13147 ** General **
Posted: 12/17/87 at 1:23 am
From: Ron Bardarson
To: TONY PARKER
About: Z280 GRIPE ## (13 lines)
Scott Moore has just applied for user status, perhaps your comments
would be better directed to him. As for msg content, the rule of
illegal activities applies ( foul language, credit/telephone card info,
etc..). I believe in everybodys right to put their foot in their mouth,
but at the same time, think that a point of view should be presented
without emotion. I have not deleted any of the Z-280 discussion and
will not, I believe that the majority of sales of the 280 will be to
Z-System folkes and wish to allow all interested parties their say.
As for your comments, if you already feel that they are too strong,
then perhaps you should tone them down until you feel satisfied ( but
you're the judge ). when entering a msg, remember that's the only
medium via which a reader may form an opinion of you, so present your
msg accordingly.
-------
Message #13151 ** General **
Posted: 12/17/87 at 2:58 am
From: Scott Moore
To: Dave Vanhorn
About: Z280 (28 lines)
Very good to hear that someone out there is playing around with the
Z280. Noted your message about the cache problem (or lack of).
Turning the cache off on this system, and looking about for programs
that will not run under cache, I too was hard pressed to find one.
One I did come across was turbo pascal 2.0, which here just sticks.
The cache problem gets activated as follows: the jump instruction that
CP/M places at 5 (bdos entry), is also used as the stack location
by many programs:
;
| Bdos |
------------ -> jump at 5 points here
| stack |
;
what happens is that a program which makes a call to $5, with the stack
empty, will first stack the address under the bdos entry, then jump
to the bdos. In Z280 cache terms, the program MAY both do a data access
(the stack push) and an instuction access in the same cache "line"
of 16 bytes. When the bdos returns, the fetch of the address to perform
the return messes up as follows: it reads only the low part of the
address, then copies the low byte to both halves of the PC, which
then crashes. The problem is dependent on where the location of bdos
is, and how much data is already on the stack.
I wasn't saying the cache bug appeared frequently, but even such a
once in a blue moon bug justifyes truning off the cache in my opionion.
Also a word to the wise (unofficially). dont run the processor at a
speed greater than 16 mhz (the xtal speed to the part).
Keep us apprised !
sam
-------
Message #13152 ** General **
Posted: 12/17/87 at 3:10 am
From: Scott Moore
To: ALL USERS
About: ZEDUX (11 lines)
I think the community does deseverve an apology from me concerning
the difficulty of getting through to Zedux for answers. I dropped
answering my phones and used an answering machine instead for the
reason I was not getting much done. This is no longer true,
and getting me between the hours of 10 am to 6pm or perhaps later
is usually possible. The number at my desk is 818-787-0113.
Be happy to discuss any issues, and would especially like to hear
from those who just want to discuss the Z280 in general.
I have been running CP/M on the Z280 since JAN of this year,
and have had extensive experience with the part.
sam
-------
Message #13153 ** General ** [reply to #13053]
Posted: 12/17/87 at 10:45 am
From: Greg Trice
To: Dave Vanhorn
About: z-280 (6 lines)
Interesting. I have had the concept of replacing the 80286 in an AT
with a Z280 and a PAL or two, plus new system roms, which would produce
a low cost Z280 machine, and all the plug in peripherals available
for the At would then be available. I may actually get round to manufacturing
such a machine (with a purpose designed motherboard). Using low cost
clone parts would keep the cost down.
-------
Message #13154 ** Z-System **
Posted: 12/17/87 at 10:45 pm
From: Ron Bardarson
To: Scott Moore
About: Z-280 (2 lines)
Why don't you upload the latest version of your file that explains
how to install your product in a Z-80 system?
-------
Message #13161 ** General **
Posted: 12/18/87 at 6:16 am
From: BEN GREY
To: Dave Vanhorn
About: Z280 Cache (3 lines)
I assume you understand that the Z280 has no need for an M1 since it
is a pipelined machine. Fetching an instruction has no meaning to the
bus either, since it will NOT be the next instruction executed. Ben.
-------
Message #13182 ** Z-System **
Posted: 12/19/87 at 1:59 pm
From: BEN GREY
To: Ron Bardarson [read 12/19/87 at 3:41 pm]
About: Z280 M1 (2 lines)
The Z280 does not issue any M1, impossible, since it does not know
when it is fetching an instruction or data.
-------
Message #13185 ** Z-System ** [reply to #13182]
Posted: 12/19/87 at 3:46 pm
From: Ron Bardarson
To: BEN GREY
About: Z280 M1 (6 lines)
So.... you need MREQ* and M1* to determine if it's an opcode fetch
or a memory read. Can't imagine anyone decoding the difference, so
I don't see the importance of the Z-280 not providing M1* during an
opcode fetch. It certainly provides M1* during int ack. Still wondering
what the problem is with the ZIP board in Kaypro's...maybe Scott will
upload his info file.
-------
***** THESE ARE FROM LADERA Z-NODE IN L.A... ***** - rc
Msg #2473 posted 12/13/87 at 12:28 am by SCOTT MOORE
To: Tony Parker About: Z280 (30 lines)
I really can't imagine where you looked. Zedux's phone is either
(818) 787-0113 or (213) 301-1935
A general update for interested parties:
Had a frank conversation with Hi-Tech, was told (and yes, I asked if
I could pass the information on) that due to problems, they were
postponing all work on the "ultra-board" until april or may 1988.
Our basic or "direct" version of our board has been shipping for 6 months
now. This has been described ad - nauseum (z280.lbr). Our only shipments
to date have been to people who are updating (industrial) Z80 controllers
to Z280 in the field (assume that any new product they would just do
a redesign without our help). As far as CP/M / OS et. all, these have
fallen into these two general cases: 1. The board is completely explained
to the purchaser, including the fact that software/hardware updates
may be required. Without fail, the boards sent out to such customers
have come back. Each and every one of them was contacted via phone.
Basically they were called on the bluff of knowing a DAMM THING about
the hardware/software involved. We found out FAST that people will tell
us ANYTHING, with the actual intent to get "a free trial". This has gotten
rapidly silly, the last customer we virtually GRILLED about his real
knowledge about hardware/software.
The MD-3:
After having an MD-3 graciously loaned to us for a month, on a whim
decided to plug the direct board into it. It came up with no modification.
However, A software mod to the BIOS needs to be done to avoid the dread
Z280 "cache bug" in the current chip. Noone stepped forward with the
nessary skills to do this (in fact, I have not seen one person with
the genuine ability to handle or even know what is in the MD-3 BIOS).
[* ahem! * - rc] I will do the conversion myself, here, hopefully
as a demontration of how easy such a conversion can be for people
with the appropriate backround. (cont)
Msg #2474 posted 12/13/87 at 12:44 am by SCOTT MOORE
To: Tony Parker About: cont (42 lines)
The thing that must be realized here is that NO ONE COMPANY, PERSON
OR DIETY has the power to singlehandedly update every CP/M / Z80
system ever made.
THE "UNIVERSAL" board:
The coprocessor version of the board has been put together and tested
in prototype form. The problem with that unit is that it is about 10
times more complex than the present board, and requires about 10kb of
software, and a VERY high density PAL. I have postponed the final version
of that board till at least january (when we have a standing promise
to ship to a paid customer).
THIS BOARD IS NOT MAGIC. It obtains better compatibility by using
(read "wasting") Z280 power. The basic rules of compatibility are:
**** READ THIS *****
;
1. Unless you use the new instructions of the Z280,
You will see no speed improvement from the
more powerfull instruction set.
;
2. Since the old Z80 instructions execute basically
the same way on the Z280 (the same number of bytes
fetched, etc). The only way to speed up the REAL
EXECUTION SPEED is to make the cycles faster.
This is the EXACT SAME PROBLEM as moving up to
a higher speed version of the Z80, which you all
know is impossible without faster memory, etc.
Z80's are avalible up to 12 mhz NOW.
;
3. The only possible improvement offered by the Z280
in speed is via the onboard cache, and that
is BUSTED on the currently shipping chip.
Despite rumors, Zilog's shipping date for the
"fixed" version is UNKNOWN, and NOT SOON.
;
End of lecture.
Anyways, I have been taking the time to update the Z280 operating
system OS/Z280 to version 3.0. In january, that system will be 2 years
old (yes, you read correctly). We remain the only users of the system,
as the current Z280 adapter users aren't OS users (as explained).
I expect to show a MD-3 version in january. [Wow! - rc] Time will tell.
If you have any questions GIVE US A CALL. Forgive the frankness,
but I am bloody sick of hearing 2nd, 3rd and nth party rumors and trash.
sam
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