5 ms·

This chap has also built a 8088 PC clone. I'm just wondering why not a 8086?

colejohnson66 3y ago
The original IBM 5150 used the 8088, as did all the clones. So, assuming the author got ideas from old schematics, they would probably use the same chip.
LukeShu 3y ago
There wasn't really an important 8086 box. The first IBM PC (1981) used the 8088. The first 8086 PCs were the discount models in the PS/2 line (April 1987), 3 years after the 80286 in the PC/AT (1984); so the 8086 was already obsolete by the time it was in a PC. And later that year (August 1987) it would be even more obsolete when an 80386DX PS/2 came out.
- MenhirMike 3y ago
  The one truly important 8086-based machine I can think of is the Japanese NEC PC-9801, so it would make some sense for someone to clone a machine like that. Though I'm not sure if I'd clone the original 9801 that kicked off the entire line or rather go for the much improved NEC V30 chip instead. (Which also powered Irem's M72 Arcade Board, which ran R-Type, and the latter M82/M84 boards that gave us R-Type II - though arguably, arcade boards aren't in the same category as home computers)
- kjs3 3y ago
  If you think the only 'important' thing in computing at that time was the IBM PC, then maybe you think there were no 'important' 8086 boxes. There was a lot more going on at the time if you were actually there working at the time.
- pwg 3y ago
  > The first 8086 PCs were the discount models in the PS/2 line (April 1987) You missed two earlier ones. The Olivetti M24 (also sold as the AT&T 6300 in the US) was released in 1983 and used the 8086 CPU. https://en.wikipedia.org/wiki/Olivetti_M24 https://en.wikipedia.org/wiki/Olivetti_M24
  - Tor3 3y ago
    Was about to say that. The M24 was the one I much preferred using during that period, before AT (286) PCs started arriving (or made affordable). There were other 8086 PCs around as well - I had a low-cost British one at home (IIRC it was called Advance 86 (EditUpd: That one was released near the end of 1983, way before any PS/2 line in 1987))
- BeetleB 3y ago
  > The first 8086 PCs were the discount models in the PS/2 line (April 1987) That doesn't sound right to me. I recall growing up with friends who had 8086 PCs, bought prior to 1987.
  - mrlonglong 3y ago
    There were two variants of Model 30 in 1987. One with 8086 and another with the 80286. They were rehashed obsolete hardware with the ill-fated MCA which was supposed to be the future, but PCI won this particular battle.
    - BeetleB 3y ago
      As mentioned by a number of others in the comments, there definitely did exist 8086 based PC compatibles prior to 1987. No one is disputing the existence of this particular model.
- mrlonglong 3y ago
  I can think of one that was significant in the UK - the Amstrad PC1512, running off a NEC V30 processor, with 512KB RAM, easily upgradeable to 640K, with options for one or two floppies. I had one myself, along with a 32MB hard card fitted into the rear expansion slots.
- dingosity 3y ago
  I had a Compaq Deskpro with an 8086. Noticeably faster than that XT. I bought it used, durt cheap when everyone else was upgrading to 286s. It worked quite well for quite some time. And the AT&T 6300 used an 8086 and the Toshiba T1200 had an 80C86. 8088's were definitely more popular among the cost-conscious, but it seemed after a couple years the clone manufacturers were making 8086 based systems for about the same price as IBM XTs.
vasac 3y ago
Is the 8086 so different from the 8088 that it requires a different BIOS?
- LukeShu 3y ago
  Yes. The external bus on the 8088 is 8-bit while the 8086 is 16-bit (which is why the 8086 wouldn't appear in a PC until the mostly-80286 PS/2 line, since the 8086 and the 80286 could use the same 16-bit PS/2 bus).
  - kjs3 3y ago
    There were numerous 8086 PC compatibles before the PS/2 or the 80286 became popular. The most famous was of course the original Compaq Deskpro, but At&t, Wang, Eagle and others did too. Yeah, the BIOS had to be aware of the difference between the 8088 and 8086 for some setup stuff, but the 8086 is at the hardware level perfectly happy to talk to an 8-bit bus and the software mostly never knew the difference. edit: And how could I forget (as mentioned by another poster in the thread) the numerous NEC PC98 machines with an 8086 which created their own industry. Sorry for slight, Japan.
  - rasz 3y ago
    and what does that have to do with BIOS? The only way you can tell 88 from 86 apart in software is speed and executing self modifying code to measure processor 4 vs 6 byte prefetch queue depth buffer size difference. https://www.minuszerodegrees.net/misc/Determining%20Processor%20Types.pdf https://www.minuszerodegrees.net/misc/Determining%20Processo...
  - mlyle 3y ago
    Around the same time, there's things like the Amstrad PPC512 (NEC V30, which is roughly 8086 pin compatible).
  - userbinator 3y ago
    That's a hardware, not a software difference. With the exception of bus speeds / timings and the differently sized prefetch queue, the 8088 and 8086 are 100% software-compatible so there wouldn't need to be any difference in the BIOS.

The original IBM 5150 used the 8088, as did all the clones. So, assuming the author got ideas from old schematics, they would probably use the same chip.

LukeShu 3y ago

There wasn't really an important 8086 box. The first IBM PC (1981) used the 8088. The first 8086 PCs were the discount models in the PS/2 line (April 1987), 3 years after the 80286 in the PC/AT (1984); so the 8086 was already obsolete by the time it was in a PC. And later that year (August 1987) it would be even more obsolete when an 80386DX PS/2 came out.

MenhirMike 3y ago
The one truly important 8086-based machine I can think of is the Japanese NEC PC-9801, so it would make some sense for someone to clone a machine like that. Though I'm not sure if I'd clone the original 9801 that kicked off the entire line or rather go for the much improved NEC V30 chip instead. (Which also powered Irem's M72 Arcade Board, which ran R-Type, and the latter M82/M84 boards that gave us R-Type II - though arguably, arcade boards aren't in the same category as home computers)
kjs3 3y ago
If you think the only 'important' thing in computing at that time was the IBM PC, then maybe you think there were no 'important' 8086 boxes. There was a lot more going on at the time if you were actually there working at the time.
pwg 3y ago
> The first 8086 PCs were the discount models in the PS/2 line (April 1987) You missed two earlier ones. The Olivetti M24 (also sold as the AT&T 6300 in the US) was released in 1983 and used the 8086 CPU. https://en.wikipedia.org/wiki/Olivetti_M24 https://en.wikipedia.org/wiki/Olivetti_M24
- Tor3 3y ago
  Was about to say that. The M24 was the one I much preferred using during that period, before AT (286) PCs started arriving (or made affordable). There were other 8086 PCs around as well - I had a low-cost British one at home (IIRC it was called Advance 86 (EditUpd: That one was released near the end of 1983, way before any PS/2 line in 1987))
BeetleB 3y ago
> The first 8086 PCs were the discount models in the PS/2 line (April 1987) That doesn't sound right to me. I recall growing up with friends who had 8086 PCs, bought prior to 1987.
- mrlonglong 3y ago
  There were two variants of Model 30 in 1987. One with 8086 and another with the 80286. They were rehashed obsolete hardware with the ill-fated MCA which was supposed to be the future, but PCI won this particular battle.
  - BeetleB 3y ago
    As mentioned by a number of others in the comments, there definitely did exist 8086 based PC compatibles prior to 1987. No one is disputing the existence of this particular model.
mrlonglong 3y ago
I can think of one that was significant in the UK - the Amstrad PC1512, running off a NEC V30 processor, with 512KB RAM, easily upgradeable to 640K, with options for one or two floppies. I had one myself, along with a 32MB hard card fitted into the rear expansion slots.
dingosity 3y ago
I had a Compaq Deskpro with an 8086. Noticeably faster than that XT. I bought it used, durt cheap when everyone else was upgrading to 286s. It worked quite well for quite some time. And the AT&T 6300 used an 8086 and the Toshiba T1200 had an 80C86. 8088's were definitely more popular among the cost-conscious, but it seemed after a couple years the clone manufacturers were making 8086 based systems for about the same price as IBM XTs.

vasac 3y ago

Is the 8086 so different from the 8088 that it requires a different BIOS?

LukeShu 3y ago
Yes. The external bus on the 8088 is 8-bit while the 8086 is 16-bit (which is why the 8086 wouldn't appear in a PC until the mostly-80286 PS/2 line, since the 8086 and the 80286 could use the same 16-bit PS/2 bus).
- kjs3 3y ago
  There were numerous 8086 PC compatibles before the PS/2 or the 80286 became popular. The most famous was of course the original Compaq Deskpro, but At&t, Wang, Eagle and others did too. Yeah, the BIOS had to be aware of the difference between the 8088 and 8086 for some setup stuff, but the 8086 is at the hardware level perfectly happy to talk to an 8-bit bus and the software mostly never knew the difference. edit: And how could I forget (as mentioned by another poster in the thread) the numerous NEC PC98 machines with an 8086 which created their own industry. Sorry for slight, Japan.
- rasz 3y ago
  and what does that have to do with BIOS? The only way you can tell 88 from 86 apart in software is speed and executing self modifying code to measure processor 4 vs 6 byte prefetch queue depth buffer size difference. https://www.minuszerodegrees.net/misc/Determining%20Processor%20Types.pdf https://www.minuszerodegrees.net/misc/Determining%20Processo...
- mlyle 3y ago
  Around the same time, there's things like the Amstrad PPC512 (NEC V30, which is roughly 8086 pin compatible).
- userbinator 3y ago
  That's a hardware, not a software difference. With the exception of bus speeds / timings and the differently sized prefetch queue, the 8088 and 8086 are 100% software-compatible so there wouldn't need to be any difference in the BIOS.