I imagine it would work, so long as the systems in question are SMP, and not some sort of AMP setup like many dual-386 and early dual-486 systems were.
Pentium was well into the SMP era, so there should be no issues at all with that machine.

Windows 2000 Professional's minimum system requirements is a Pentium 133 MHz with at least 32 MB of RAM. Microsoft back then recommend a Pentium II 300 MHz with 128 MB of RAM.

If you could get Windows 2000 to install on such a dual 486 CPU setup, expect very poor performance.
Installing it on a dual Pentium 1 CPU setup might prove more interesting.

You could, however, install Windows NT 4.0 on a dual 486 CPU setup and, yes, it can take advantage of both CPU's (with some caveats as mentioned in the previous post).

Standard Def Steve wrote on 2021-07-28, 20:28:

I imagine it would work, so long as the systems in question are SMP, and not some sort of AMP setup like many dual-386 and early dual-486 systems were.
Pentium was well into the SMP era, so there should be no issues at all with that machine.

I thought that all 486's were ASMP? Or were there some SMP setups?

Windows 2000 Professional's minimum system requirements is a Pentium 133 MHz with at least 32 MB of RAM. Microsoft back then rec […]
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Windows 2000 Professional's minimum system requirements is a Pentium 133 MHz with at least 32 MB of RAM. Microsoft back then recommend a Pentium II 300 MHz with 128 MB of RAM.

If you could get Windows 2000 to install on such a dual 486 CPU setup, expect very poor performance.
Installing it on a dual Pentium 1 CPU setup might prove more interesting.

You could, however, install Windows NT 4.0 on a dual 486 CPU setup and, yes, it can take advantage of both CPU's (with some caveats as mentioned in the previous post).

I have Windows 2000 on the 486 system in my signature and it's really not too bad. It's usable.

Standard Def Steve wrote on 2021-07-28, 20:28:

I imagine it would work, so long as the systems in question are SMP, and not some sort of AMP setup like many dual-386 and early dual-486 systems were.
Pentium was well into the SMP era, so there should be no issues at all with that machine.

Early Multi-CPU systems with i386 processors were supported by Windows NT 3.1, I vaguely remember.
I've seen a picture once of such a monster in an issue of Byte Magazine, I believe.
Not sure about Windows NT 3.51 or higher, though.

chublord wrote on 2021-07-28, 20:44:

Standard Def Steve wrote on 2021-07-28, 20:28:

I imagine it would work, so long as the systems in question are SMP, and not some sort of AMP setup like many dual-386 and early dual-486 systems were.
Pentium was well into the SMP era, so there should be no issues at all with that machine.

I thought that all 486's were ASMP? Or were there some SMP setups?

I have an old VTech dual-486 machine up in the attic that I'm 100% 80% sure is an SMP system. Haven't played with it in years, but iirc it had NT 3.1 on it.

Jo22 is making me question that system's true SMP capabilities though. If NT 3.1 indeed supports AMP systems, then my old VTech may very well be one of those. Till now I had always assumed that all flavors of NT were SMP-only, since I don't believe there was ever an industry standard way of implementing AMP.

I know for sure, though, that Windows 2000 only supports SMP.

All NT OSs supported 2 processors out of the box....

^ +1 Yes, that's right, afaik.

I've tried to find some information about that i386 multi-CPU system and was partly succesful. 😀
It seems that the original Compaq SystemPro from '89 used i386 CPUs and was supported by the original relase of NT 3.1.
As it seems, it used the second processor for some i/o work, while programs ran on the primary processor.

Source: https://en.wikipedia.org/wiki/Compaq_SystemPro

"If you expand the criteria to include systems where the two CPUs are not on the same circuit board,
the Intel ISBC 86/12 from 1979 is a Multibus-compatible single board computer.

Later, the Compaq SystemPro from 1989 supported up to two 33 MHz 386 processors, also on their own cards,
and could run Windows NT 3.1, but this version of SystemPro only supported asymmetric multiprocessing (ASMP).
SystemPro/XL from 1992 which was based on the 486/50 was SMP.

Another interesting product is the Evergreen Rev to SMP from 1995 which
allows you to plug two 486 CPUs into a single socket on the motherboard." - snips-n-snails

..

"Well, AFAIK the SystemPro was asymetric as the second CPU was dedicated to I/O operation,
run by driver code, while Windows NT did only run on the first one." – Raffzahn

Source: https://retrocomputing.stackexchange.com/ques … x86-motherboard

Heh, well an XT is AMP too then, when it's got a MFM controller with a Z80 on it to handle the i/o 🤣 ... I have also heard tell there's some modems with embedded 80186 chips on, but I haven't found one yet.

null

I thought it was confirmed that the Rev to SMP was vapourware.

null

Probably worked okay for computationally hard stuff with small amounts of data that fit in the L1, but a bit of a notchy niche.

Anders- wrote on 2021-07-29, 16:17:

Anonymous Coward wrote on 2021-07-29, 11:33:

I thought it was confirmed that the Rev to SMP was vapourware.

Agreed. I can't understand how it could work at all, 2 cpu's talking with the motherboard using the pins of only 1.
(if it it worked, it would be a huge bottleneck)

Many dual processor systems shared the bus in one way or another though cache and memory might be doubled up