I thought I have the same computer M4 434S but it turns out it is not quite the same.

I'm missing a few jumpers and the M4 434S has on board audio from OPTi, mine hasn't that is why it seems so clean.

I put in a DX2 66, it sees it as DX2 but CPU speed is still 50MHz. I moved the jumpers in various combinations but still 50.

I have lots of vintages but on this one I could not find any information whatsoever.
I even wrote to Olivetti but got back a standard answer asking me to go to a dealer.

I have a suspicion that pin header near the CPU socket with the simple two-wire jumper plugged into it is a VRM header. Notice the heavy traces and largish bypass caps in the same vicinity too...

It's possible for 5V CPU's it was simply bypassed with those wire jumpers, and required a 3.3v VRM to be installed when low-voltage CPUs were used.

Meister wrote:

I'm missing a few jumpers and the M4 434S has on board audio from OPTi, mine hasn't that is why it seems so clean.

Compare it to a Compaq presario 7170 Pentium 90 system board, with UMC chipset as well: ten times more SMD resistors surrounding every chip. I suppose 486 architecture is way simpler, as show by those mini Zida Tomato motherboards.

You can consider this as an option to upgrade to DX4:

http://www.ebay.com/itm/Vintage-CPU-Intel-Ove … MUAAOSwr~lYpAug

5x86-133

http://www.ebay.com/itm/Kingston-Turbochip-CP … 0kAAOSwWxNYtMya
http://www.ebay.com/itm/Vintage-CPU-Processor … OMAAOSwopRYmihC

Found the jumper after watching a short presentation clip of an Italian guy on youtube
If someone has the same family of motherboards and want to change the speed from 25 to 33, it's the 2 jumpers in the picture below.

No need for upgrade for me. I have 2x 386, 2x 486, 2x P1, plenty speeds to choose from. 😀
Just wanted to build the best dx2 66 and since this was the best AT case in house, I mounted a 2MB VLB video card instead of the 256kb on board, swapped the factory sound card with a Gravis Ultrasound Classic
and doubled the RAM. It works like a dream.