dionb wrote on 2018-09-22, 13:30:

Scali wrote:

My thoughts here are that the 8086 and 80186 were rather 'unfortunate' products in the history of the PC.
That is, they were 16-bit CPUs in an era where the 'real' PC platform was still 8-bit. 16-bit ISA slots and chipsets were not introduced until the PC/AT with the 286 CPU. So I have never seen a 'full' 16-bit machine based on an 8086 or 80186. They were generally XT-class machines with a 16-bit CPU shoehorned in for some reason, but not taking full advantage.

Given the 8086 precedes both the 8088 and PC/XT itself, it's rather the case that the PC was a rather unfortunate low-end, (for 1981) low-budget implementation of the x86 architecture than anything else. The only reason it became dominant was marketing.

There were certainly full 16 bit designs based on the 8086, Olivetti's M24 (sold as AT&T 6300 in the US) comes to mind. The 16 bit bus was fully functional and utilized for video and memory cards. Theoretically any other type of card could also have been made for it - but as no one else used the same 16b bus and it was completely different (electrically and physically) to the later AT bus, there were no further peripherals made for it. However that had nothing to do with technical implementation - which was decidedly superior to PC and XT - but simply due to market conditions.

Someone mentions the NEC PC98 series in this thread. It didn't use anything resembling isa slots, but rather c-bus, which plugged into the backside of tne puter. I want to say it's a full blown 16 bit bus as the 1st generation PC 9800 (9801?) used an 8086. As did the gringo variant, the NEC APC III. Don't forget the original APC which was a technological Kraken. It's card cage had a lot of resemblance to the Multibus and OMG IS THIS TBREAD BECOMING CONVOLUTED 😀

aquishix wrote on 2018-09-22, 17:34:

I've come across a couple of examples of 8086-based PCs, and at least one of them had 16-bit (non-ISA) buses. This is the only […]
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Scali wrote:

My thoughts here are that the 8086 and 80186 were rather 'unfortunate' products in the history of the PC.
That is, they were 16-bit CPUs in an era where the 'real' PC platform was still 8-bit. 16-bit ISA slots and chipsets were not introduced until the PC/AT with the 286 CPU. So I have never seen a 'full' 16-bit machine based on an 8086 or 80186. They were generally XT-class machines with a 16-bit CPU shoehorned in for some reason, but not taking full advantage.

Since there have been various homebrew projects to create 8088 machines, wouldn't it be interesting if such a project were extended to an 8086 or 80186 and create a proper 16-bit machine, to unlock the full power and features of these CPUs? Just to see 'what could have been'? 😀

I've come across a couple of examples of 8086-based PCs, and at least one of them had 16-bit (non-ISA) buses. This is the only one I can remember at the moment:

https://en.wikipedia.org/wiki/PC-9800_series

Of course it would be Japanese. I'd never heard of this thing when I was a kid, but I've run across mentions of it recently because of my love of vintage & retro gaming. (There are some cool anime games that were original to the PC-98 that made their way to the standard PC world.) The bus slots on the motherboards for it look like 8-bit PC slots because they're roughly the same length and have only one segment, but they have a different number of pins and are noted to be 16-bit.

Apparently it was really an IBM decision NOT to use the 8086 and NOT to use 16-bit slots, until, as you said, the AT debuted with the 286 CPU.

Strange, in my opinion. But maybe it made sense from an economic standpoint for IBM at that particular time. They did set the standard which has evolved into what we still use today, so it's hard to say they were wrong, exactly.

The PC98 was a long lived Japanese standard. The bus HAD to (if not initially) be 16 bit as you find it on members all the way up to pentium era.

Scali wrote on 2018-09-22, 17:50:

The story I heard was that both the 8088 and Motorola 68000 were in the race when IBM was designing the PC. Ultimately they chos […]
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aquishix wrote:

Apparently it was really an IBM decision NOT to use the 8086 and NOT to use 16-bit slots, until, as you said, the AT debuted with the 286 CPU.

The story I heard was that both the 8088 and Motorola 68000 were in the race when IBM was designing the PC.
Ultimately they chose against the 68000 because it would require them to develop a more expensive 16-bit infrastructure, and possibly develop their own custom chips, because the 68000 ecosystem was still in its infancy (Apple decided to go with the 68000 in the Lisa at the same time, so we can see what happened there).
The 8088 was chosen because it was backward-compatible with the Intel 8085 peripheral chips. IBM already had experience building 8085 systems using cheap off-the-shelf parts (see the IBM Datamaster), and they could recycle a lot of that for the PC.
For this reason the 8086 was probably never even considered as an option (if you are going 16-bit anyway, picking the 68000 over the 8086 is a no-brainer).
Here's a nice story on that: https://archive.org/stream/byte-magazine-1990 … e/n451/mode/2up

aquishix wrote:

They did set the standard which has evolved into what we still use today, so it's hard to say they were wrong, exactly.

Depends on who you ask, I suppose.
Leads us back to the Betamax-VHS discussion. VHS won, but wasn't technically superior to Betamax. It was more about price, availability, convenience etc.
I think the same goes for the IBM PC. I personally think that IBM 'accidentally' made the PC a success, because it was so easy to clone. Ultimately it was the clones that made the PC platform a success, because IBM itself was always overpriced and underperforming.
It was all the clones that drove prices down and performance up, to the point where the line between business computer and home computer was completely blurred.

IBM didn't utterly shun the 68000. It was the core of the infamous Lab computer, which I think was as expensive as a Lisa initially.

The 8086/88 gets a really bad rap in retrospect. Stupid, slow, segmented memory. But you had to remember it was really 2 chips in 1. Compare minimal mode and maximal mode. In minimal mode it was essentially an 8085 with a 64k memory ceiling. And while the 8088 wasn't a fully 16 bit chip, it still had effectively a 20 bit address space allowing 2^20 or 1 mb of memory. It was a bridge between 2 worlds and may habe been exactly what the market needed.

aquishix wrote on 2018-09-23, 15:04:

Scali wrote:

My thoughts here are that the 8086 and 80186 were rather 'unfortunate' products in the history of the PC.
That is, they were 16-bit CPUs in an era where the 'real' PC platform was still 8-bit. 16-bit ISA slots and chipsets were not introduced until the PC/AT with the 286 CPU. So I have never seen a 'full' 16-bit machine based on an 8086 or 80186. They were generally XT-class machines with a 16-bit CPU shoehorned in for some reason, but not taking full advantage.

http://www.vcfed.org/forum/showthread.php?282 … odesl-25-amp-30

Is this an example of the kind of system you were referring to?

Link don't work.

kokerich wrote on 2018-09-27, 00:13:

In Yugoslavia Novkabel launched in 1985 a ET188A PC-XT compatible machine based on a 80188 CPU. Machine was fully compatible wit […]
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In Yugoslavia Novkabel launched in 1985 a ET188A PC-XT compatible machine based on a 80188 CPU.
Machine was fully compatible with PC-XT clones with MS-DOS or CP/M.
They chose 188 cpu because it had integrated peripherals so design of the motherboard was easier.
Technical Specifications:
CPU: Intel 80188 running at 8MHz
ROM: 8 KB custom made BIOS
RAM: 256KB (ET-188) or 512 KB (ET-188A), expandable up to 640 KB
Operating system: MS-DOS 3.20
Secondary storage: 2 x 5.25’’ 360KB floppy drive or 5.25’’ 360KB floppy drive + 22MB Tandon hard disk
Display: CGA compatible adapter (color text 40x25, 80x25 or graphic 320x200, 640x200) or Hercules compatible adapter (monochrome 80x25 text or graphic 720x348)
Sound: beeper
I/O ports: DE9 video output, RS-232, parallel port, keyboard

I will have 1 of these. I'm half yugoslavian/hrvatska croatian.

burnutec wrote on 2023-11-26, 10:13:

Hello to you all , i'm also interested in creating the 80186 based system, i have the highest performing variants of this cpu , with the correcponding socket, plcc68 , i know it needs to be fed 2x the actual cpu clock speed , but not much more right now , i would spend time reading and designing the circuitry that will make use of this cpu, but i feel if i do it alone without any help it might take forever. Is there anyone who also wants to create such machine eventually?

Yes but our goals may differ enough to imcite thermonucleat conflict. Let's talk though.

Tiido wrote on 2023-11-26, 13:30:

Do you want to make just a 186 based system or you want to make a IBM PC (or some other existing standard) compatible machine ?

Who knows. The 80188 is available in abundance on ebay rigjt now. I bought a batch from this vendor andnmay buy more. If anyone needs help obtaining these message me.

rmay635703 wrote on 2023-11-27, 01:28:

Exactly, and on this subject, I had access to the leftovers from beige box XT class system motherboards in college. Amongst the […]
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Tiido wrote on 2023-11-26, 13:30:

Do you want to make just a 186 based system or you want to make a IBM PC (or some other existing standard) compatible machine ?

Exactly, and on this subject, I had access to the leftovers from beige box XT class system motherboards in college. Amongst these fully pc/XT clone compatible motherboards were 8086 and 80186 boards with 8 bit ISA and 16 bit banks of ram. Boards were all baby AT form factor . Guessing they all went to ewaste.

I believe most were mid to late 80’s
From what I was told none of the 186 chips onboard components were used.

But I’ve seen old timers grumble that certain late revision 80186 chips were made to be more pc/xt compatible (maybe Chuck)

So it’s possible you could reuse on chip components if you get a late rev 186, Chuck says so.

IMG_4788.jpeg

Maybe better to use 80188. Overcome 80186 fetish.

Tiido wrote on 2023-11-27, 07:36:

All the internal peripherals can be ignored, although BIOS will need to set them up so that way first (but aware software can mess with that stuff if it really wanted).

But as far as IBM PC goes, you need the timer, IRQ and DMA controller along with KBC that all work exactly the same way as original parts, same memory map and of course BIOS that provides all the same functions in same way. It is a significant amount of work to make a IBM PC compatible machine.

Why is dma chip needwd? Spexifically for compatibility? Dma is mostly for disk access and such. Doesn't seem to have anything to do with compatibility (Tandy 1000 doesn't come with it as stock). Tandy 2000 eliminates it altogether. Nice to have for speed but for compatibility?

kant explain wrote on 2023-11-28, 00:20:

Jo22 wrote on 2018-09-22, 09:51:

That's right. Though IBM PC compatibilty wasn't all that important in the first half of the 1980s. Originally, system makers ass […]
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That's right. Though IBM PC compatibilty wasn't all that important in the first half of the 1980s.
Originally, system makers assumed that industry kept going the CP/M way of hardware independence,
so MS-DOS compatibility was considered good enough for a while. Unfortunately, things went different and programmers started to
do a lot of bare metal programming, assuming everyone had an IBM PC. This broke compatibility for a lot of early systems,
which were only DOS and partially PC-BIOS compatible. Anyway, I'm no PC/XT expert. Just summing up what I learned from reading old magazines.

🤣 lOL compatibility was extremely important in every part of the 80s (except 1980, non IBM puters were all the rage). Thing is if you bought a Tandy 2000 say, and had a few dozen titles to choose from, you maybe were fat (as was I), dumb (as I was definitely), and happy for a while. Until you tried to boot Starflight 🙁. A lot of hot titles were available. There's a sourceforge or github site full of Tandy 2000 specific s/w and docs if you google.

But not IBM-compatiblity.

CP/M compatiblity was the thing in the low 1980's.
Even MS-DOS had to be kinda compatible to CP/M (because 86-DOS/QDOS was inspired by CP/M's API).
Later it was DOS compatiblity. Microsoft supplied adaptions for almost each supplier within DOS 1.x, like PC-DOS.
Suddenly the IBM PC got mainstream (perhaps due to the royalty-free PC-BUS "ISA") and things changed. While the compatiblity to the IBM PC got important, Phoenix developed a BIOS that was free from any IBM code but has cloned the interface and Microsofts sold its own MS-DOS to the users of the clones. That was likely in the mid of the 1980's.
But even the API of MS-DOS has been changed. Do you remember accessing files with FCBS?
With the IBM AT in the mid 1980's it was still IBM who set the standard. However, with the 386 IBM lost the lead... to a "COMPAtible Quality" manufacturer.

kant explain wrote on 2023-11-28, 01:01:

Why is dma chip needwd? Spexifically for compatibility? Dma is mostly for disk access and such. Doesn't seem to have anything to do with compatibility (Tandy 1000 doesn't come with it as stock). Tandy 2000 eliminates it altogether. Nice to have for speed but for compatibility?

DMA was used for memory refresh, floppy disk drive and hard disk drive.

kant explain wrote on 2023-11-28, 00:52:

aquishix wrote on 2018-09-23, 15:04:

http://www.vcfed.org/forum/showthread.php?282 … odesl-25-amp-30

Link don't work.

That's the problem with the internet and referring to a 5 year old thread.
Links may get invalid if the webmaster did not care about compatiblity.

kant explain wrote on 2023-11-28, 00:29:

Total loads were used as microcontrollers. It wasn't a failure at all, was just repurposed. The IBM Professional Graphics Controller used an 8088. I think there were 3 clones of that card(s). One was made by Vermont Microsystems, the only clone I have. It uses an 80188. There is another graphics card out there, which may be more of an early gen locker that uses an 80186. I forget the specifics.

I think the problem was that Intel expected the 186/188 could be the successor to the 86/88.
During development of the 186/188 Intel didn't even had in their mind that IBM would pair the 8088 with peripheral chips that were made for the 8085!

Look at the inefficient bus access of the 8088. It took ages to load a command into its 4 byte prefetch queue. And its address bus was multiplexed with the data bus too!

Off the top of my head there was the 8089, which was a bus master? Hope I didn't screw that up. I'm really not aware of which chips Intel intended as companions to the 8086/88.

I have so many irons in the fire. But I was looking at a guy's videos whereinhe buildis a small 80c86 based system on a breadboard! Everyone should watch that. I'll find it and edit this thread.

No I'm braindead. He uses an 80c88:

https://www.youtube.com/watch?v=VvyUAaRTsww

kant explain wrote on 2023-11-28, 04:11:

Off the top of my head there was the 8089, which was a bus master? Hope I didn't screw that up. I'm really not aware of which chips Intel intended as companions to the 8086/88.

The 8089 indeed was a companion to the 8086/8088.

kant explain wrote on 2023-11-28, 01:01:

Why is dma chip needwd? Spexifically for compatibility? Dma is mostly for disk access and such. Doesn't seem to have anything to do with compatibility (Tandy 1000 doesn't come with it as stock). Tandy 2000 eliminates it altogether. Nice to have for speed but for compatibility?

If it were to be IBM compatible it needs the DMA controller, or you will not have sound with almost any of the widely supported PCM capable sound cards such as SB series.

Disruptor wrote on 2023-11-28, 01:40:

DMA was used for memory refresh, floppy disk drive and hard disk drive.

Yup, in theory you could do without, as the IBM PCjr demonstrates (as well as early Tandy 1000 models, where a DMA controller could be installed as part of a memory upgrade).
It wouldn't be 100% PC-compatible, but you'd get away with it in practice.
Hardly anyone ever exploited the fact that DMA can be used for accessing disks 'in the background', and the only other common use of the DMA controller was to drive DACs on sound cards.
Memory could be refreshed via other circuitry (PCjr has its video memory shared with system memory, so the video circuit refreshes the memory as it accesses it, which was common for 8-bit machines in the day), or by using SRAM which does not need to be refreshed.

Disruptor wrote on 2023-11-28, 01:40:

DMA was used for memory refresh, floppy disk drive and hard disk drive.

On c't 86, DMA might also have been used for video.
My father vaguely remembered that.

https://www.ebay.com/itm/231799363235?epid=12 … ABk9SR_TrhNCCYw

80188. So cheap. That poor bloke has been listing them since 2015 at least. I bought 5, will buy more.

Yes using a fully 16 bit 80186 intrigues me also. But for beginning stages of tinkering I want to use the 80188. Can always somewhat easily alter design (of what exactly I am not sure. IBM compatibility is a nice goal).