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Amiga computer related discussion => General chat about Amiga topics => Topic started by: glitch on September 21, 2015, 10:21:22 PM
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The C128 and Z80 CPU ...or Intel 8088?
So as I sit here testing CP/M on a TRS-80 Model 4P, I began thinking about the Commodore 128 and CP/M mode. I had a few instances to play with it, but never really gave it a fair shake. To me, the C128 was always best used in C64 mode and occasionally in C128 mode. I would boot up in CP/M mode more to test disks and CP/M compatibility than to ever use it for anything serious. Has anyone here actually used the C128 and CP/M? CP/M seemed to me to be past its prime when the C128 rolled out.
That got me thinking.
What if noticing that, CBM had instead made the C128 with an Intel 8088 (or preferrably an 8086) instead of the Zilog Z80 CPU?
To me, I think this would definitely encouraged more sales. More parents buying ONE machine instead of two - C64/C128 mode for the kids and PC mode for "serious" work. Perhaps this would have launched the company in a completely different direction. It could have seriously hurt the Amigas sales too, or the development of the bridgeboards at least.
In hindsight I know there are about a thousand things we could have wished CBM management had done differently, but this one got me going today...
Thoughts?
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I wish I knew what to add.
I did not use CPM much on the 128 either.
I wonder if Vice 128 uses CPM.
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IMHO,
Well the 8086 required 16 data lines, that makes no sense in an 8-bit computer.
Commodore already had a CP/M cartridge for the C64, so they had a history of hardware development there (disk formats did suck).
While CP/M could run on an 8088, the 8088 was far more expensive than a Z80 that was there to run CP/M -- also the CP/M OS and software was proven. Commodores implementation of CP/M was always tertiary behind the C64 and C128 -- no one bought a C128 to run a non-graphical OS. I believe they just threw in the Z80 and CP/M as a publicity gimick to give weak justification to productivity on the C128 to people who did not know the C128 has such software.
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I believe a C65 would have been better.
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I believe a C65 would have been better.
Obviously.
I never really got the idea of including the Z-80 either.
CP/M was pretty dated and lacked graphics support.
So what was the point?
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Maybe they bought them for something else and had nowhere to use them knowing how things were run :)
I had C128 , it should have had built in disk drive (that would probably need another CPU) at that point and a mouse.
Only good thing is that case looked much better and more professional.
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CP/M 3.0 was only 2 years old when the 128 came out and there was a huge library of software available for it including business and productivity software that was seriously lacking on the C64.
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Maybe they bought them for something else and had nowhere to use them knowing how things were run :)
I had C128 , it should have had built in disk drive (that would probably need another CPU) at that point and a mouse.
Only good thing is that case looked much better and more professional.
The c128dcr had a built in 71, Both commodore and CMD made mice for the c64/128
Lt Kernel(SP?) and CMD made hard drives.
The z80 was chosen on purpose not for just cpm, but it was a necessary chip to make all 3 modes live together,iirc it used the z80 for its early startup.
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I read that there were a load of Timex Sinclair TS1000s at Commodore after people bought the $49 systems to get a $100 rebate on a C64. I think they had shipping containers full of them onsite and they were also used as doorstops.
I guess you could clarify with Bill or Dave but I understand that one of the doorstops donated it's CPU when they were designing the C128. Had it not been for the doorstops they probably wouldn't have considered adding CP/M mode but it was concenieent and probably sounded like a good idea when presented to mangement and the marketing people.
No Idea if any of the CPUs from the thousands of TS1000s they had were recycled for use in productions C128s or if they just used brand new chips.
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CP/M 3.0 was only 2 years old when the 128 came out and there was a huge library of software available for it including business and productivity software that was seriously lacking on the C64.
This. I used CP/M 3+ on my 128D frequently, but mostly for my first programming classes. Small C, some COBOL and Pascal compilers. It worked great, and I could write to floppies which my instructor could read with her computer.
I used a bunch of other software for various things. I downloaded a lot of software, some from Q-Link's CP/M area but almost everything else from GEnie, and some things from BBSes.
I have discussed various CP/M ports on and to other CPUs, like 68000 and 9900. But the prevalence of Z80 software almost negates native ports and rather encourages good Z80 emulation.
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What if noticing that, CBM had instead made the C128 with an Intel 8088 (or preferrably an 8086) instead of the Zilog Z80 CPU?
CBM did make the desktops, like the Commodore Colt, PC-10, PC-20, PC-30, (and more), and 286, 386, and 486 laptops.
Truly,
Robert Bernardo
Fresno Commodore User Group
http://www.dickestel.com/fcug.htm
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I guess you could clarify with Bill or Dave but I understand that one of the doorstops donated it's CPU when they were designing the C128.
I've never heard that story from either Bil or Dave.
No Idea if any of the CPUs from the thousands of TS1000s they had were recycled for use in productions C128s or if they just used brand new chips.
Since 4 to 5 million C128's were produced, having a few thousand chips from TS1000's would not fulfill production needs. Anyways, nothing has been said about how many TS1000's were exactly turned in.
Truly,
Robert Bernardo
Fresno Commodore User Group
http://www.dickestel.com/fcug.htm
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...no one bought a C128 to run a non-graphical OS.
There were those who bought the C128 so that they could run the graphical OS, GEOS, in 80-column mode.
Instead of the 40-column C64 GEOS,
Robert Bernardo
Fresno Commodore User Group
http://www.dickestel.com/fcug.htm
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I believe a C65 would have been better.
FYI, C128 development began in 1984 with the release of the C128 in 1985. C65 development began and stopped in 1989-1990, due to the fact that 8-bit development was a dead-end in those later years.
The C64 lasting in production until 1992,
Robert Bernardo
Fresno Commodore User Group
http://www.dickestel.com/fcug.htm
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I've never heard that story from either Bil or Dave.
From On The Edge:
To fix the problem, Herd required the C128 to start at memory address zero, but the 8502 started elsewhere. "One night, everybody left and it was broken," says Herd. "During the night, I said, 'I have no way to fix this, unless we startup by not starting at that address.' I said, 'Hey, Von. The Z80 chip starts from zero, doesn't it?' He said, 'Yup.' I said, 'Cool. I need somebody wire wrapping tonight.'"
The hour was too late to purchase a Z80 chip, so Herd looked elsewhere. "Everybody had doorstops that were actually Sinclairs," he recalls. "I went and tore open my doorstop because we didn't own a Z80 chip in the place."
I don't believe they re-used the Z80's in production models though. After hearing about how the C64 was put into production for Christmas however, nothing would surprise me :D
Putting in an 8088 would likely have not helped much as making the computer MSDOS compatible to any real degree would have been impossible. An NEC V20 would have been better as it could run CPM in it's 8080 mode, but you can also run 8086 software. It lacks the extra Z80 instructions but most CPM software is compatible with 8080 anyway (Z80 is an 8080 clone with added instructions). It might not add much, but you also wouldn't really lose anything.
The C128 was like the A3000. Both were based on custom chips from a previous design, but with extra glue around them because there was no time/money/inclination to improve them. If the C128 had an 80 column VIC that could work when the CPU was running at 2mhz then it would have been a worthwhile upgrade & much closer to the C65 but still C64 compatible.
The C65 was designed during the time when AAA was in development hell, I can understand why in that environment the C65 project would have made some sort of sense and it probably would have sold if it was cheap enough. Another couple of engineers also went off and pushed through the Pandora project, which turned into AGA.
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Thanks for quoting that. I gave away my copy of On The Edge some time ago and didn't remember exactly what was written.
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Thanks for quoting that. I gave away my copy of On The Edge some time ago and didn't remember exactly what was written.
I still have mine, but I forgot where it was written anyway. I only found it by googling:
c128 z80 doorstop
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The c128dcr had a built in 71, Both commodore and CMD made mice for the c64/128
Lt Kernel(SP?) and CMD made hard drives.
The z80 was chosen on purpose not for just cpm, but it was a necessary chip to make all 3 modes live together,iirc it used the z80 for its early startup.
This is the way I remember it too. Using an 8088 in the C-128 makes little to no sense at all.
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This is the way I remember it too. Using an 8088 in the C-128 makes little to no sense at all.
It might have made sense to design it in at the start, although an NEC V20 would make more sense as you could still run CPM on it. However you would want either want to increase the MMU address space or connect it on the other side of the MMU so you could address all the memory from 8088 mode using segments.
The magic voice startup problem was solved because the Z80 doesn't start by fetching the same address as the 6502, but neither does the 8088/V20. So it should have been an equally good workround, except I doubt anyone at commodore was using an 8088 computer as a doorstop at the time.
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From On The Edge:
To fix the problem, Herd required the C128 to start at memory address zero, but the 8502 started elsewhere. "One night, everybody left and it was broken," says Herd. "During the night, I said, 'I have no way to fix this, unless we startup by not starting at that address.' I said, 'Hey, Von. The Z80 chip starts from zero, doesn't it?' He said, 'Yup.' I said, 'Cool. I need somebody wire wrapping tonight.'"
The hour was too late to purchase a Z80 chip, so Herd looked elsewhere. "Everybody had doorstops that were actually Sinclairs," he recalls. "I went and tore open my doorstop because we didn't own a Z80 chip in the place."
Heh, I will reconfirm with Bil. As Bil and Leonard Tramiel said at CommVEx, the Brian Bagnall book(s) is/are not entirely accurate.
Truly,
Robert Bernardo
Fresno Commodore User Group
http://www.dickestel.com/fcug.htm
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Heh, I will reconfirm with Bil. As Bil and Leonard Tramiel said at CommVEx, the Brian Bagnall book(s) is/are not entirely accurate.
If you watch all of Bil's talks back to back you should detect some inconsistencies. It's no wonder the book is not accurate.
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The Amstrad CPC 6128 also shipped with CP/M. I never used it much either than for disk work. Think did have a spread sheet prog I used to use on it occasionally. Always preferred Amstrad BASIC
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CP/M 3.0 was only 2 years old when the 128 came out and there was a huge library of software available for it including business and productivity software that was seriously lacking on the C64.
All of it text based with no graphics or sound.
Still a step backwards.
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Oh yes, I'm not trying to stir up any which OS is better argument - I was just thinking of what if the 8088 was used instead and what different path MAY have unfolded - had they perhaps made the C128 into some PC compatible too.
I remember seeing the DEC Rainbow and thinking it was cool as well.
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Oh yes, I'm not trying to stir up any which OS is better argument - I was just thinking of what if the 8088 was used instead and what different path MAY have unfolded - had they perhaps made the C128 into some PC compatible too.
I remember seeing the DEC Rainbow and thinking it was cool as well.
Glad to meet someone else that remembers that system.
It was pretty cool, but really expensive for a PC clone.
Also had the first AND processor I had ever seen inside.
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I was just thinking of what if the 8088 was used instead and what different path MAY have unfolded - had they perhaps made the C128 into some PC compatible too.
It would have been impossible to make it PC compatible. Using the 8088 would also not have solved the issue why the Z80 was put in there to start with. In most of Bil's videos he says it was because the CP/M cartridge exceeded the amp budget and the decision to start the Z80 first instead of the 6502, to fix magic voice autostart, came later.
Bil learnt what C64 compatibility meant when they built the C128. IBM learnt what PC compatibility meant when they built the IBM PCjr. A C128 with an 8088 would have been less compatible than the PCjr, which itself was a failure.
PC compatibility never helped the Amiga either.
CP/M was more suited because of hardware fragmentation, each manufacturer made hardware to their own design and so applications had to go through the OS. While there was some fragmentation in the MS-DOS market to start with (Chuck Peddles Victor/Sirrius for example) by 1985 the market demanded that every piece of CGA/DMA/floppy/hard disk/sound hitting software would work.
An NEC V20 on the other hand would have allowed CPM-80 and CPM-86 applications to run & we could even have seen a port of GEM rather than GEOS.
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It would have been impossible to make it PC compatible. Using the 8088 would also not have solved the issue why the Z80 was put in there to start with. In most of Bil's videos he says it was because the CP/M cartridge exceeded the amp budget and the decision to start the Z80 first instead of the 6502, to fix magic voice autostart, came later.
Bil learnt what C64 compatibility meant when they built the C128. IBM learnt what PC compatibility meant when they built the IBM PCjr. A C128 with an 8088 would have been less compatible than the PCjr, which itself was a failure.
PC compatibility never helped the Amiga either.
CP/M was more suited because of hardware fragmentation, each manufacturer made hardware to their own design and so applications had to go through the OS. While there was some fragmentation in the MS-DOS market to start with (Chuck Peddles Victor/Sirrius for example) by 1985 the market demanded that every piece of CGA/DMA/floppy/hard disk/sound hitting software would work.
An NEC V20 on the other hand would have allowed CPM-80 and CPM-86 applications to run & we could even have seen a port of GEM rather than GEOS.
Impossible? Nonsense.
My firm made the PT68K4 PC compatible with a V20 based board.
The Amiga could be made PC compatible with a series of boards that topped out with a '386 based board (and those have a much better resale value than PCs based on the same processors).
Of course a system could have been built with both PC and C64 compatibility.
And the PCjr's video modes lived on in the Tandy 1000 series.
So that machine did have some significance.
GEOS and GEM? Almost as ugly a solution as CP/M.
MS-DOS and Windows compatibility have far more utility.
Most of your post appears to be unsupported opinion, unless I am reading it wrong.
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@Glitch:
A far better choice would've been an NEC V20 or NEC V30 chip, as it would've allowed MS-DOS in addition to CP/M, but you have to remember those chips probably cost significantly more than a Zilog Z80A at that time the C= C128 was introduced in January 1985 (according to Wikipedia). C='s choice of a Z80A was a cheaper CPU chip then an 8088, V20, or a V30. The C128 was already more expensive than the C= C64 computer. Price was a big thing back then. Also, don't forget that there was most likely licensing fees for MS-DOS, too, and that would've added to its final cost, as well as the C128 development team needing to get MS-DOS properly interfacing on the C128. Hindsight is always 20/20.
On another note, why don't you install AmigaZ80 from AmiNet instead of testing CP/M on a TRS-80 Model 4P? I uploaded that file to AmiNet.
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CBM did make the desktops, like the Commodore Colt, PC-10, PC-20, PC-30, (and more), and 286, 386, and 486 laptops.
Truly,
Robert Bernardo
Fresno Commodore User Group
http://www.dickestel.com/fcug.htm
So if you consider those projects, wouldn't a C64 expansion card have made sense?
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A cheaper 8088 or 8086 processor would have provided CP/M-86 compatibility, and MP/M-86 compatibility with a possible upgrade to Concurrent DOS if CGA/VGA compatibility was implemented via a VLSI.
When the C128 was in its planning stages custom chips were becoming quite common.
While the earlier chips in the C64 and Amiga required a large investment to create, the latter custom chips in devices like the Tandy 1000 and the Color Computer 3 were significantly less costly.
AND as Commodore owned MOS...the C128 wasn't a particularly adventurous design (and for that matter Bill wasn't that great a designer).
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Impossible? Nonsense.
My firm made the PT68K4 PC compatible with a V20 based board.
The Amiga could be made PC compatible with a series of boards that topped out with a '386 based board (and those have a much better resale value than PCs based on the same processors).
In 1985 you would need register level CGA/floppy/dma/irq/serial etc. You couldn't reuse anything from the C64, so it would essentially be a PC and a C64 in the same box (like https://en.wikipedia.org/wiki/Amstrad_Mega_PC).
The Amiga at least could display the video from a PC using it's graphics chip, so a combined hardware and software approach allowed it to work. But to make it compatible with games you had to use an actual ISA graphics card. So it was just an Amiga and PC in the same box, it didn't really save any money and you could get better PC's.
Sure you could stick an 8088 in the C128 and it would have access to 64k at a time. No software would know how to display anything on the screen or access more than 64k. The original PC came with 64k so you could run software that worked on that as long as it only used BIOS and DOS calls to access hardware (which a lot of software didn't).
The Z80 came quite late in the C128 design, so there was never a time when it would have made sense to design something radically different with an 8088 that allowed more than 64k at a time.
Of course everything is possible given enough time and money, but keeping to the C128 selling price and spending very little in chip design and it was impossible.
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@Rabbi:
Thank you for the AmigaZ80 link! That will be fun too. I am actually in the process of upgrading the RAM on the Model 4P to 128K. I am in the process of getting it ready for sale on eBay (shameless plug if anyone is interested...) and wanted some additional disks to include. I downloaded some other LS-DOS disk images and even blew the dust off my old high school books and entered some lines of FORTRAN to test out the compiler I found.
I learned FORTRAN on an old PDP-11 - THAT my friends was pain. Our teacher as brilliant as she was, wanted us to learn to code on cards and enter them with a card reader and output would be sent to the teletype. We then switched to the terminals - at least that was easier to debug. After that we switched to the lab full of CBM PET machines.
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In 1985 you would need register level CGA/floppy/dma/irq/serial etc. You couldn't reuse anything from the C64, so it would essentially be a PC and a C64 in the same box (like https://en.wikipedia.org/wiki/Amstrad_Mega_PC).
The Amiga at least could display the video from a PC using it's graphics chip, so a combined hardware and software approach allowed it to work. But to make it compatible with games you had to use an actual ISA graphics card. So it was just an Amiga and PC in the same box, it didn't really save any money and you could get better PC's.
Sure you could stick an 8088 in the C128 and it would have access to 64k at a time. No software would know how to display anything on the screen or access more than 64k. The original PC came with 64k so you could run software that worked on that as long as it only used BIOS and DOS calls to access hardware (which a lot of software didn't).
The Z80 came quite late in the C128 design, so there was never a time when it would have made sense to design something radically different with an 8088 that allowed more than 64k at a time.
Of course everything is possible given enough time and money, but keeping to the C128 selling price and spending very little in chip design and it was impossible.
Ah! My apologies. You guys are frequently good for some education.
"The Z80 came quite late in the C128 design..."
That explains SO much.
I've always blamed Bill for the kludged together nature of the C128.
Its like they tacked a cheap CP/M board onto an existing design, which appears to be what happened.
I'd always thought that was what Bill intended at the outset.
Which should explain my bad attitude about him.
He and Dave must have felt a constant sense of butt hurt dealing with Commodore's management and their perpetual penny pinching.
They probably should have just left the Z-80 out (or the 6502).
If you compare the C128 to something like an MSX system, the C128's implementation of the Z-80 processor comes off looking really lame.
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The C= 128 should never have existed as late as it was (less than 1 year before the Amiga in early 1985). C= should have put a SID chip in the Amiga and paid to have a highly optimized C64+6502 emulator written in 68000 assembler. Perfect upgrade path to the Amiga plus the SID adds new sound synthesizing functionality to the Amiga.
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The C= 128 should never have existed as late as it was (less than 1 year before the Amiga in early 1985). C= should have put a SID chip in the Amiga and paid to have a highly optimized C64+6502 emulator written in 68000 assembler. Perfect upgrade path to the Amiga plus the SID adds new sound synthesizing functionality to the Amiga.
I love SID tunes, but I'm glad that the Amiga had Paula. A full speed C64 emulator with decent compatibility on a 68000 Amiga is impossible..
The C64 lived on for another 7 years, so there was definitely a market for an 8 bit computer. The C128 just turned out too expensive and not enough people cared about C128 or CPM mode.
He and Dave must have felt a constant sense of butt hurt dealing with Commodore's management and their perpetual penny pinching.
I'm not sure that Bil was that bothered about the penny pinching, he seems to quite enjoy the challenge. The problem at that time was marketing, the 8563 chip designer and his boss who cancelled the C128 because it was taking too much time. If Jack had stayed then these problems would have resolved themselves with much less impact to the C128 schedule.
Without Bil you would have got this instead http://www.floodgap.com/retrobits/ckb/secret/d128.html An evolution of the P500 that was dropped because commodore needed as many VIC and SID chips as they could make to stuff in C64's.
The C128 with just a z80 would have been a disaster. After the C128 shipped someone worked on an upgraded design that could run the Z80 faster. I don't know if that ever survived and whether it would be practical as a retro-fit.
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I love SID tunes, but I'm glad that the Amiga had Paula. A full speed C64 emulator with decent compatibility on a 68000 Amiga is impossible..
Paula and SID both are possible without too much overlap in functionality. It is very easy to throw an FPGA SID (or 2) in an FPGA Amiga motherboard now days if it would sound acceptable as all digital. SID in an Amiga back then would have probably required lowering the voltage more but that was happening with later revisions of the C64 anyway.
I believe the 68000 could have emulated the 6502/6510 CPU o.k. but the chipset emulation would have been difficult at full speed. The Amiga has its custom chips to offload the 68000 so maybe it would have been good enough. Perhaps the biggest hurdle at that time was the buggy AmigaOS. Different size and capacity of floppy drives didn't help either.
The C64 lived on for another 7 years, so there was definitely a market for an 8 bit computer. The C128 just turned out too expensive and not enough people cared about C128 or CPM mode.
I would have continued to manufacture the C64 until demand dropped too much. Developing and marketing the C128 was a waste of resources which could have been used for the Amiga.
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I would have continued to manufacture the C64 until demand dropped too much. Developing and marketing the C128 was a waste of resources which could have been used for the Amiga.
According to google, in 1985 the C128 was $300 and the A1000 was $1295.
There was room in the market. If anything they should have stopped selling the C64 and cost reduced the C128 (which they started doing but then cancelled it and kept selling cost reduced C64's instead).
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I am not sure I would not have favored a 2MHz 6509 with no Z-80.
Faster operation just makes sense.
For that matter, if you eschew compatibility, Commodore could have used a 2MHz 6809 which has a lot of advantages over a 6502 based CPU.
One of my primary reasons for favoring the Amiga is that system's use of a decent Motorola processor.
I have never been that impressed with MOS' cut rate offerings.
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I am not sure I would not have favored a 2MHz 6509 with no Z-80.
Accessing memory with the 6509 was a nightmare, the C128 can run the 8502 at 2mhz so you didn't lose anything. Ideally they should have made an 80 column VIC. It would need to fetch multiple bytes per clock so that the CPU didn't get starved of bus activity. But at least then you could run faster than 1mhz without turning off the screen.
A 6809 would have at least doubled the price. I like the 68000 but it's the only Motorola CPU that is really any good, if it hadn't been so good then commodore wouldn't have paid the premium.