I own a couple of PS2 to AT adapters. One of them works fine with the couple of boards I have used it on. The other one does not. The faulty one doesn't work because despite the pin conversion, the outer ring wasn't grounded.

I can't remember the exact continuity check that failed, but I assume that there was no connection linking the outer ring of the AT side plug to the inner ring of the PS2 side plug in the adapter. It is possible your AT keyboard requires this connection for proper grounding, and your adapter isn't providing it.

CkRtech wrote:

I own a couple of PS2 to AT adapters. One of them works fine with the couple of boards I have used it on. The other one does not. The faulty one doesn't work because despite the pin conversion, the outer ring wasn't grounded.

I can't remember the exact continuity check that failed, but I assume that there was no connection linking the outer ring of the AT side plug to the inner ring of the PS2 side plug in the adapter. It is possible your AT keyboard requires this connection for proper grounding, and your adapter isn't providing it.

thanks for the advice, after reading it, i did more tests on my adapter cable pictured below.

1) Cable only: All the inner pins on one side of the cable have continuity to the other side of the cable.
2) Cable only: The Outer ring (orange) DOES NOT have continuity from one side to the other orange side on the cable.
3) Cable only: there is NO continuity between PIN4 ground, with outer rings Orange.
4) Cable + Motherboard: all the INNER pins on the cable also have continuity to motherboard contacts.

pin1: is clock
pin2: is data
pin3: is reset (not used)
pin4: Ground
pin5: 5v VCC

So what you are saying is that it can be solved by using a wire to connect both outer rings in organge?

Or using a cable to connect the outer ring orange to pin4 ground?

I would connect outer ring to outer ring. "Orange to orange" in your case. Leave the pins as they are.

Check the keyboard fuse.

i took another keyboard that was ps2 and connected it with the adaptar and it finally detected it and was able to setup the bios!!!!!!!!

I don´t know why this motherboard does not like my ibm MODEL M (SDL) modded with a ps2 cable

very of strange that award bios 4.20 is only 1 page, for example the screen says hit "page down" and "page up2 for other pages but that doesnt work, is award bios 4.20 only 1 page with such few options?

Chances are Your IBM Model M keyboard is for an XT motherboard, which is not compatible with AT motherboards,
even though they use the same connector.

I was pretty sure the XT model M is an autoswitch keyboard and can work on AT systems.

Based on what I have read, the Model M keyboards draw a good amount of power. It is possible that your mobo doesn't provide the adequate power it needs.

CkRtech wrote:

Based on what I have read, the Model M keyboards draw a good amount of power. It is possible that your mobo doesn't provide the adequate power it needs.

probably this is the main reason
I got a model M very cheap and mint condition but it was DSL connector and the owner lost the cable.
So reading online i did a mod to it, soldered a PS2 extension cable and converted it into a PS2 model M

but the motherboard probably doesnt provide enough power, the model M works on a pcchips 486 motherboard tho.

the bios, my good, it was the first time i see a 1 page bios. 🤣