When you compare each CPU, you can see that JP16 is always set to "closed" or "1-2" for 3x cpus (and the 5x86) while the DX2s have it to "open"

Though it might be something completely different, all we can do here is guessing ...

Deksor wrote:

When you compare each CPU, you can see that JP16 is always set to "closed" or "1-2" for 3x cpus (and the 5x86) while the DX2s have it to "open"

Frankly, I thought it was a voltage selector (3.45v vs 5v) since it's open for all DX2s, but your comment made me recall that some AMD DX2s were 3.45v. However, I tried it in "open", and the benchmark didn't change.

Though it might be something completely different, all we can do here is guessing ...

It's just that I've seen a lot of people mention this board on Vogons, so I think someone might be able to give me some insight.

Another thing that may help would be to update the bios. My Aopen AP43 needed one in order to make my 5x86 to work or else mine would hang at POST (it was working configured as a DX4) though that shouldn't change the frenquency

BIOS R2.30 is the latest version available I'm afraid. I also have that board, but it's the 5V only version (no voltage regulator) so I cannot test my 5x86 there.

This link may be of help however:

http://www.cpu-collection.de/?l0=co&l1=amd&l2=5x86

In particular:

"Since having a clock multiplier of four was not part of the original Socket 3 design, AMD made the 5x86 look for a two times setting from the motherboard and interpret that as four times instead. In other words, to use the 5x86 you want to set the motherboard to the 2x setting. This will actually cause the 5x86 to run at 4x."

Deksor wrote:

Another thing that may help would be to update the bios. My Aopen AP43 needed one in order to make my 5x86 to work or else mine would hang at POST (it was working configured as a DX4) though that shouldn't change the frenquency

I had the exact same thing with the AP43 board. No way it would run the 586 cpu at 2x/4x but it ran fine on the 3x33 and 3x40 setting as an Amd dx4 cpu.
As soon as i set the 2x setting it went all bananas on me and would hang right after post or run extremely slow. A bios update made it all go away and the board is running 4x 40mhz at the moment, fast and stable.

So i don't know what it is with these cpu's but bios support can be very important. This usually is not a problem with the Cyrix 5x86 (as far as i know).

Looks like AOpen is even hosting BIOS files for this board, and 2.30 is really the last version. This version is dated '93, so it's obvious that I'll never get the board to show 5x86 in POST.

Furthermore, it looks like L1 cache is in write-through mode. I can set L2 to write-back in BIOS settings, but L1 options are greyed out, so I assume it should be configured through jumpers? Can this explain why right now the CPU doesn't even reach DX4-100 levels?

So it looks like I need to a) find 2x option b) change cache to write-back.

To find out how to enable write-back, just compare the settings for the amd DX4 write-trough and write-back ^^

jheronimus wrote:

Looks like AOpen is even hosting BIOS files for this board, and 2.30 is really the last version. This version is dated '93, so it's obvious that I'll never get the board to show 5x86 in POST.

Furthermore, it looks like L1 cache is in write-through mode. I can set L2 to write-back in BIOS settings, but L1 options are greyed out, so I assume it should be configured through jumpers? Can this explain why right now the CPU doesn't even reach DX4-100 levels?

So it looks like I need to a) find 2x option b) change cache to write-back.

When options are greyed out it will be slow, happened also on the ap43 board. Your best option is to set it as a dx4-120 (3x40mhz). This way those options are probably not greyed out and you don't need bios support. It will still be fast and with 16kb cache. On the ap43 even 3x50 was a stable option but memory timings had to be set to pretty slow.