pentiumspeed wrote on 2023-04-12, 22:47:

Careful of this motherboard this contains a CMD possibly 640 which is a issue with IDE reliability.

It's only a test system so I am not too bothered, further I only run Windows NT V4.00 SP6a which has code to deal with this (see CTRLTEST.pdf) and it's been fine for the past two years.

Today I tried to use my Cyrix Cx486 DX2-66, but I can't get the system to post, it does post OK with my 5x86-100GP @ both 100 MHz and 120 MHz.

For the DX2 I used the same converter, changed the multiplier from x3 to x2, set the FSB to 33MHz and when I power on I get nothing on the screen and no beeps. Is there likely to be something else I need to change or is the DX2 likely dead please?

I've got this board or a very similar one. It didn't get used back at the tail end of 486 usefulness because I had it down as a PITA. Picky with RAM configs, only took certain CPU. That was with trying to keep up with the end of the 20thC though, "fixed in time" to the mid 90s it's probably usable for DOS stuff. Mine might find a purpose in life as an "add 486 to somewhere" project.

BitWrangler wrote on 2025-04-07, 14:30:

only took certain CPU

Thank you for your post and I suspect the "only took certain CPU" was if you didn't have an interposer, I have one and the only CPU that I have that "won't play" is the Cx486 DX2-66. The attached shows all the CPUs that work.

red-ray wrote on 2023-03-24, 23:09:

I now have 2MB on video ram

Since upgrading to 2MB I keep wondering if I can plug an ISA card into the RHS slot that is ISA sized, but actually meant to be used for a riser card with 3 x ISA slots on it. Is there any way to find out, other then to try it and hope? I just checked and my EtherLink III fits. Ideally I would get a riser card, but thus far have not found one.

I am also wondering which ISA VGA cards have > 2MB of RAM. I have a Kelvin-64, but that only has 2MB so would need to get another one.

red-ray wrote on 2025-04-23, 14:34:

Since upgrading to 2MB I keep wondering if I can plug an ISA card into the RHS slot that is ISA sized, but actually meant to be […]
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red-ray wrote on 2023-03-24, 23:09:

I now have 2MB on video ram

Since upgrading to 2MB I keep wondering if I can plug an ISA card into the RHS slot that is ISA sized, but actually meant to be used for a riser card with 3 x ISA slots on it. Is there any way to find out, other then to try it and hope? I just checked and my EtherLink III fits. Ideally I would get a riser card, but thus far have not found one.

I am also wondering which ISA VGA cards have > 2MB of RAM. I have a Kelvin-64, but that only has 2MB so would need to get another one.

My investigations into that slot went like... DEC circa 1995, personality slot, 486 LPX type board, looks like ISA but???

So everything I look at says it's ISA, I have not yet powered mine with an ISA card in there though.

Any ISA graphics is a downgrade though. Greater than 2MB ISA cards only really existed for AutoCAD, specialist and thousands of bucks new, may not work for DOS modes, may not be useful in Windows.

BitWrangler wrote on 2025-04-23, 14:57:

So everything I look at says it's ISA, I have not yet powered mine with an ISA card in there though.

Any ISA graphics is a downgrade though. Greater than 2MB ISA cards only really existed for AutoCAD, specialist and thousands of bucks new, may not work for DOS modes, may not be useful in Windows.

Thank you for your reply, I am inclined to wait and see what happens when you do, might it be any time soon please?

I don't really care about DOS, just Windows NT V4.00 SP6a, and as long as it will display 1280 x 1024 x >= 65,536 colours @ 60Hz I will be happy. On the odd occasion I need to boot DOS I can always swap the the on-board GPU.

Maybe I will get a PCI i486 board, one with PS/2 KB + Mouse, I wonder what the most RAM I could have is, I know 128MB is possible, and wonder is 256 MB? A Dual Socket one would be very tempting, which i486 CPUs support SMP?

I don't think any 486 or early pentiums did SMP, it was a different setup for the dual and quad boards. ASMP maybe. Earlier 486DX dual or quad boards would have been optimised for Netware or other vendor network server duties, not sure if they are particularly NT friendly. I am thinking actual SMP features did not arrive until the 2nd wave of socket 5 pentiums, when 120/133 were released, then you probably have to check the S-Spec to make sure.

Thank you for your reply, I think the oldest Intel SMP system I have come across recently had an ASUS PCI/I-P54NP4 (Neptune) + Intel Pentium (P54C) 90MHz [B1] @ SX909 + Intel Pentium MP (P54C) 90MHz [B5] @ SX957 and yes, the two CPUs did really have different S-Specs!

I know that Sequent made SMP 486 systems and suspect back then I did some testing on one, but I can't really remember.