I remember seeing one of those 3.1 versions on Ebay a while back, but I got a 2.11 instead which seems to work fine. You are right, there were no manuals
anywhere on the internet for the 3.1
I don't know what cpu's You have but maybe try a dx2-66 instead. I know the 2.11 needs modding for proper voltage support for AMD 5x86-133.

How about posting a high-res photo on here, someone may have an idea.

EDIT - Just found the manual http://www.phantom.sannata.ru/forum/file.php? … &key=1374780731

The jumpers are different! you may have just saved my life!

Maybe somehow the jumpers effect how the cpu talks to the memory, hence my intermittent memory beeps.

I have it up and running! though it wont boot to windows at 160mhz, hangs as soon as it tries to load the boot sector.

Tried upping voltage but it wont post with anything other than stock voltage setting. have to live with 133 for now.

any tricks on that front?

Good news that it works. The only "trick" I know of is heatsink and fan at 160mhz. You could also try relaxing chipset and ram timings as running the FSB at 40mhz
instead of 33mhz might be putting too much of a strain on things.
As You have it working, It might be a good idea to upload the bios file here for anyone else that comes across one of these 3.1 versions.

You could also try EDO ram again, but as the 2.11 boards only post with FPM then it probably won't work.

I am running an HSF, one of the ones that the CPU slides into, and then turn the heatsink and it clamps onto the cpu, with a very light layer of thermal compound on the contact area. The heatsink itself remains cool to the touch at 133.

I think my 256kb of 20ns cache chips may be limiting me to 133mhz at the moment. perhaps I should get 512k of 15ns cache?
I could be totally wrong and see if it works if i set everything to the slowest settings in bios, but I would probably end up slower than stock timings at 133 wouldn't i?

not sure how to read my bios file do i need to change the bios jumper to read it? Should i even bother upgrading to 1.72f version?

I have 64mb of FPM memory in it now, I'm not too concerned about a few mb/s loss in performance. Mostly going for bragging rights in my 486 club, haha.

All You need is a program that can read the bios file, Dos or Windows. Leave the jumper alone.
I wouldn't try flashing the 1.72f version as How do You know it will work with the 3.1 board?

Good point, I suppose after I post the 3.1 bios maybe someone else can check to see if there are any differences that can cause issues between it and the 1.72f bios.

These old 486 mobo's generally do not have flashable bios chips on them. You would need spare eprom or eeprom chips and a burner to try and flash another bios.
My 2.11 board had the non eraseable bios chip so I just burn't a new one and it all works well.

The point of me asking You to copy the bios information and upload is so the community has a copy should someone's mobo bios die.