P2 350 has Vcore 2.0V I think.

Depends on the mainboard. I think these rely on the mobo's VRM to automatically detect the CPU (in your case, I doubt any of those two will run 100 and 133FSB Coppermines (66FSB Celeron Coppermines do run, from what I experienced...) as they were usually made with Mendocinos in mind.) so if the mobo is made with Coppermine support in mind, it should set voltage accordingly.

PcBytes wrote on 2022-11-13, 11:32:

Depends on the mainboard. I think these rely on the mobo's VRM to automatically detect the CPU (in your case, I doubt any of those two will run 100 and 133FSB Coppermines (66FSB Celeron Coppermines do run, from what I experienced...) as they were usually made with Mendocinos in mind.) so if the mobo is made with Coppermine support in mind, it should set voltage accordingly.

Yep, they do. The slotket will just pass the unmodified voltage request "signal" from the installed CPU to the VRM. If the CPU asks for a voltage that the VRM cannot supply, it'll not output anything at all.

It's not uncommon that the VRM on old boards can supply the lower voltages newer CPU:s the board wasn't made for needs though. Best way to find out would be to check the datasheet for the VRM controller on your particular board. Or simply determine by testing, as mentioned the VRM won't output anything if it gets a request it doesn't understand, there's no risk of frying anything.

Toaster999 wrote on 2022-11-13, 11:23:

I have been donated two adaptor cards (see pics) no brand or jumpers so I guess not that great but I thought I would mess about with them. No voltage adjustment - I have a dual slot 1 motherboard with 2x pentium 2's in the (350/100) so what voltage would that be? 1.8v I think?
Any help would be awesome - even if it's a don't bother with it!

The first slotket marked PII CPU card VER 1.5 is an ECS / PCChips product. This is an early 1999 edition and meant to support Mendocino Celerons only. One of the jumpers may (or may not) change the setting to fsb 100. From the photo it appears as if the slot teeth are not gold plated and this type of slotket is better not left in a motherboard slot over a longer period of time.
It is mentioned here:
https://forums.anandtech.com/threads/help-any … slotket.690316/

The second slotket is a Jetway product and also meant to support Mendocino Celerons only.
It is mentioned on this old french website:
https://www.hardware.fr/articles/58-2/asustek-abit.html
https://www.hardware.fr/articles/58-3/a-trend … jetway-msi.html

Great knowledge guys! Always impressed with how helpful people have been on this site - thks!