interesting topic but there were so many "IBM PC Compatibles" or clones around that it would be difficult to narrow it down, especially by the late 80's .

You might be right about it being a 286, though i remember a lot of 8086's still being around back then too

one thing you could do is look up scanned late 80's computer magazines online, the adverts alone are illuminating as to what was around and also there's quite a bit of nostalgia to be had 😀

High Density floppies suggest an AT.
Also, 3.5" floppies were rare in XT clones.

On the other hand, hard to believe in an AT being originally without HDD.
Around 1989/90, only very low-end PCs were sold without HDD, and that meant XTs.

And no, I've never seen anybody referring to an 8086 machine as an AT.
AT may mean 286.
AT may mean any 286+ with 16-bit ISA and the related stuff: double PIC, double DMA, CMOS/RTC, etc.
8088, 8086, 188, 186, V20, V30 - they are always coupled with 8-bit ISA, single PIC, single DMA... so, they are NOT ATs.

Grzyb wrote on 2023-06-14, 09:21:

High Density floppies suggest an AT. Also, 3.5" floppies were rare in XT clones. […]
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High Density floppies suggest an AT.
Also, 3.5" floppies were rare in XT clones.

On the other hand, hard to believe in an AT being originally without HDD.
Around 1989/90, only very low-end PCs were sold without HDD, and that meant XTs.

And no, I've never seen anybody referring to an 8086 machine as an AT.
AT may mean 286.
AT may mean any 286+ with 16-bit ISA and the related stuff: double PIC, double DMA, CMOS/RTC, etc.
8088, 8086, 188, 186, V20, V30 - they are always coupled with 8-bit ISA, single PIC, single DMA... so, they are NOT ATs.

This made me stop and think.. My next PC was an Amiga, and the 880K 3.5" drive in it was not inferior to the one in our first PC at all. So quite possibly the drives (both!) may have been Double Density instead! Went back and fixed that.

If the floppies were Double Density, it's pretty safe bet that was an XT.
Even the original IBM AT from 1984 shipped with a 1.2 MB drive - it's extremely unlikely to find an AT clone without High Density.

Grzyb wrote on 2023-06-14, 09:40:

If the floppies were Double Density, it's pretty safe bet that was an XT.
Even the original IBM AT from 1984 shipped with a 1.2 MB drive - it's extremely unlikely to find an AT clone without High Density.

What about an 8086? An XT would imply an 8088, but I remember my dad recommending against one in favor of an x86 CPU.

The original IBM XT had 8088.

Later XT clones had various CPUs...
common: 8088, V20, 8086, V30
uncommon: 188, 186, V40, possibly others

The most common PCs with 8086 were:
IBM PS/2 model 25 and 30
Amstrad PC 1512 and 1640

Grzyb wrote on 2023-06-14, 09:21:

8088, 8086, 188, 186, V20, V30 - they are always coupled with 8-bit ISA, single PIC, single DMA... so, they are NOT ATs.

8086, 80186, V30? certainly not always. You had an 8086 with a 16-bit bus in the Olivetti M24/AT&T PC6300 and in some other semi-clones (especially Soviet ones apparently), but the design was proprietary and certainly not AT-compatible. Most 80186 machines sacrificed true PC compatibility to take advantage of the CPU's onboard peripherals, so they had no reason to stick with 8-bit ISA.
But for generic PC clones, yeah - 8086 was most often seen with an 8-bit bus. In principle nothing was stopping anyone from plopping an 8086 into a 16bit AT-class design, there was just no incentive to do so.

HD floppies are less conclusive, since there were plenty of XT-compatible FDCs with BIOS extensions to provide hi-density support. I've certainly seen them in XT clones back in the day. Just not terribly common, because hi-density media didn't become prevalent until the XT clones were on their way out.

VileR wrote on 2023-06-14, 10:02:

8086, 80186, V30? certainly not always. You had an 8086 with a 16-bit bus in the Olivetti M24/AT&T PC6300 and in some other semi-clones (especially Soviet ones apparently), but the design was proprietary and certainly not AT-compatible. Most 80186 machines sacrificed true PC compatibility to take advantage of the CPU's onboard peripherals, so they had no reason to stick with 8-bit ISA.
But for generic PC clones, yeah - 8086 was most often seen with an 8-bit bus. In principle nothing was stopping anyone from plopping an 8086 into a 16bit AT-class design, there was just no incentive to do so.

OK, there were even 8086 machines with S-100 bus, that predated the IBM PC.
But if we're talking about PC clones with ISA - it was always 8-bit ISA, never 16-bit ISA.

Juko ST Turbo PC's were still being sold in the late 80's. Possibly you either had a V20 or V30 CPU in your system. A 12 MHz V20 CPU could still run most games from that era without an issue.

Wouldn't most XTs be 8088 rather than 8086, though?

H3nrik V! wrote on 2023-06-14, 13:03:

Wouldn't most XTs be 8088 rather than 8086, though?

That was my understanding, and how we named things as well. At least locally, an XT was an 8088 CPU system, and an AT was an x86.

Earlier in the thread someone mentioned 8086 and 80186 XT-Clones, and that boggles my mind. How does that work? You can't just drop an x86 CPU on an 8-bit bus motherboard, it won't work. For it to worki you need a 16-bit bus for memory at the very least even if you only have 8-bit ISA slots. Being restricted to 8-bit peripherals does not make a system XT-Class in my view. I believe that is why my dad kept referring to an 8086 as an AT-compatible. As far as I can remember there was a significant performance difference between 8088/8086 at same clock speeds by virtue of memory bandwidth alone!

I'd be very interested in hearing other people's views about this. Are 8086 computers XT-class? AT-class? Or altogether different? I know there are IBM PS/2 systems that are 8086 and ISA based (Model 20 and 30 IIRC?) are they referred to as IBM PC compatibles (ie XT compatible) or AT compatbiles?

What was sold when is heavily, and I can't stress how much, country and region dependent.
In my country for example having a weak currency back then XTs were sold brand new well into 1991 and 1992, when people in other countries were discussing whether to get a 386 or a 486.
So everyone's memories while accurate might not be very helpful in this particular search

Grzyb wrote on 2023-06-14, 09:21:

And no, I've never seen anybody referring to an 8086 machine as an AT.
AT may mean 286.

My Nixdorf 8810 M35 is/was being advertised as "AT compatible", despite it having an 8088.
Typo? Maybe the AT compatibility was on BIOS level, only? 🤷‍♂️

https://www.computerwoche.de/a/nixdorf-zaeumt … dia-auf,1163375

https://www.cpu-galaxy.at/complete_systems/Ni … ixdorf_8810.htm

appiah4 wrote on 2023-06-14, 13:13:

H3nrik V! wrote on 2023-06-14, 13:03:

Wouldn't most XTs be 8088 rather than 8086, though?

That was my understanding, and how we named things as well. At least locally, an XT was an 8088 CPU system, and an AT was an x86.

Yesn't. XT and AT are terms by IBM. They're tied to architecture, rather than CPU.
There was an XT 286, for example.

The AT architecture differs in these terms from XT:
- Real-Time Clock, CMOS and CMOS Setup
- HD floppy support (500 KB/s)
- new AT keyboard interface
- full-fledged "ISA" Bus (PC/AT bus in case of real IBM PC/ATs)
- AT BIOS with new functions
- different memory locations (hard disk controllers, vector tables etc)
- twice the DMA and interrupt controllers (in cascade)
-..

Edit: IBM used full 8086 CPUs in its low-end PS/2 series.
PS/2 was a fork of AT architecture, more or less.
But it turned out to be a dead end. It wasn't fully backwards-compatible, also.

While the machine in question was not likely to be one, the Japanese PC-98 standard also used 8086 CPUs (or their V30 counterparts).

Other than that, I agree with the general sentiment in this thread, which seems to be: it's unlikely that the machine was an 8086 one (especially if it was a generic clone, rather than some branded OEM machine), but not entirely impossible. 8086 machines did exist.
But the most likely explanation is that people have become so accustomed to the 'x86' nomenclature, that they retroactively think their first machine was an 8086, as they had completely forgotten about the 8088, and may no longer know that an 8088 was a common 8-bit variation of the x86, but may think it's not an x86 at all.

appiah4 wrote on 2023-06-14, 13:13:

That was my understanding, and how we named things as well. At least locally, an XT was an 8088 CPU system, and an AT was an x8 […]
Show full quote

H3nrik V! wrote on 2023-06-14, 13:03:

Wouldn't most XTs be 8088 rather than 8086, though?

That was my understanding, and how we named things as well. At least locally, an XT was an 8088 CPU system, and an AT was an x86.

Earlier in the thread someone mentioned 8086 and 80186 XT-Clones, and that boggles my mind. How does that work? You can't just drop an x86 CPU on an 8-bit bus motherboard, it won't work. For it to worki you need a 16-bit bus for memory at the very least even if you only have 8-bit ISA slots. Being restricted to 8-bit peripherals does not make a system XT-Class in my view. I believe that is why my dad kept referring to an 8086 as an AT-compatible. As far as I can remember there was a significant performance difference between 8088/8086 at same clock speeds by virtue of memory bandwidth alone!

I'd be very interested in hearing other people's views about this. Are 8086 computers XT-class? AT-class? Or altogether different? I know there are IBM PS/2 systems that are 8086 and ISA based (Model 20 and 30 IIRC?) are they referred to as IBM PC compatibles (ie XT compatible) or AT compatbiles?

I recently came across some 286 motherboards with 8-bit ISA slots only. This was also a bit confusing when we (a couple of us in our local vintage community) saw these but, early 286 motherboards probably wouldn't benefit much from a 16-bit ISA bus (particularly if you simply upgraded your old XT PC to a 286 and carried over your old interface cards). Peripherals were expensive back then.

8086/8088 CPU's are both tied to the XT architecture. Both CPU's can only address up to 1 MB and are 16-bit internally but the 8086 has an external 16-bit data bus as well. A good example of such a system is the Olivetti M24/AT&T 6300. However, back in those days, the slot layout wasn't yet standardised (released in 1983 before the IBM AT).

The 80186 was more focused on embedded systems and was never intended to be the successor to the 8086/8088 CPU from a PC perspective (although, there were some PC's sold with a 80186 CPU).

The Wikipedia articles on the 8086, 80186 & 80286 CPU's provides more detailed information.

Jo22 wrote on 2023-06-14, 14:52:

Yesn't. XT and AT are terms by IBM. They're tied to architecture, rather than CPU. There was an XT 286, for example. […]
Show full quote

Yesn't. XT and AT are terms by IBM. They're tied to architecture, rather than CPU.
There was an XT 286, for example.

The AT architecture differs in these terms from XT:
- Real-Time Clock, CMOS and CMOS Setup
- HD floppy support (500 KB/s)
- new AT keyboard interface
- full-fledged "ISA" Bus (PC/AT bus in case of real IBM PC/ATs)
- AT BIOS with new functions
- different memory locations (hard disk controllers, vector tables etc)
- twice the DMA and interrupt controllers (in cascade)
-..

Yes, but the XT/286 is a misnomer, as it is basically an AT architecture, it supports pretty much everything you listed here under 'AT'.
Only the case is that of an XT.

Another possibility is that I am completely misremembering the exchange, and my dad was warning his friend against buying an AT and instead going for an XT (possibly because the AT was probably excessively pricy at that time). He is still adamant that our first PC was an 8086.. And maybe an 8086 8-bit computer was referred to as an XT as well I don't know how much a price difference there was between an 8088-8, an 8086-8 and an 80286-10 in say '89, for example?

I was only 9 years old at the time, and I wish I had a better understanding of the market, it sounds like a fascinating time to be into computers. I was only interested in games, and kept complaining that we didn't have an Amiga instead 🤣

Scali wrote on 2023-06-14, 14:56:

Jo22 wrote on 2023-06-14, 14:52:

Yesn't. XT and AT are terms by IBM. They're tied to architecture, rather than CPU. There was an XT 286, for example. […]
Show full quote

Yesn't. XT and AT are terms by IBM. They're tied to architecture, rather than CPU.
There was an XT 286, for example.

The AT architecture differs in these terms from XT:
- Real-Time Clock, CMOS and CMOS Setup
- HD floppy support (500 KB/s)
- new AT keyboard interface
- full-fledged "ISA" Bus (PC/AT bus in case of real IBM PC/ATs)
- AT BIOS with new functions
- different memory locations (hard disk controllers, vector tables etc)
- twice the DMA and interrupt controllers (in cascade)
-..

Yes, but the XT/286 is a misnomer, as it is basically an AT architecture, it supports pretty much everything you listed here under 'AT'.
Only the case is that of an XT.

I know. I just meant to say that CPU type and XT/AT aren't always tied to each others.
A better example would be upgrade boards, like the Intel Inboard/386.

They upgraded XT systems to 386 level, but the motherboard still stayed XT.
Just a single DMA and IRQ controller were available, as it was before.

Windows 3.0, for example, thus needed heavy patching to work at all on the Inboard/386.

Edit: Processor upgrade boards from 8088 to 80286 also were popular for a while.
There were at least 5 models on the market, I vaguely remember an article.
Some had a toggle switch on the bracket to switch between 8088 and 80286.

And like the Inboard, they didn't change the XT motherboard.
The 8088 CPU was removed and replaced by a socket with a ribbon cable attached to it.
The 8088 then was moved to the 80286 upgrade card were it was waiting to be used for PC compatibility (the toggle switch).