This chipset says it's 2.2v core & 3.45 I/O, so what do I set the motherboard to?

Uhh...What motherboard and CPU do you have?

I have a few different boards & a few different chips, what difference does it make? You have to set the voltage on the motherboard according to what processor you have but I don't know if I should be setting it to the core voltage or the I/O voltage. I'm thinking it's the I/O voltage but I'm not sure.

To answer your question though...
Motherboards
K6XV3+/66 Rev B
ASRock K7VT2
EP-8KTA
& there is another board but it's not what we are primarily working on because it's older & it doesn't have a model or brand name listed anywhere.

Processors
AMD AUD900 Duron 900
AMD-K6-2/450AHX (2.4V Core/3.3 I/O)
AMD-K6-2/550AGR (2.3V Core/3.3 I/O)
& we have some other ones too but you get the picture.

Now the Duron 900 and/or the ASRock K7VT2 is blown out for sure (owner tried installing 2 different types of RAM at the same time). The Duron 900 will only work in the ASRock K7VT2 or the EP-8KTA & I am currently trying the AMD K6 550 in the K6XV3+/66 Rev B but I need to know what to set the voltage to on the motherboard regardless if I am working with the K6XV3+/66 Rev B board or the EP-8KTA board (there are blue switch boxes with 5 or 6 switches on the board that are specifically for setting the voltage on the board).

Not all CPU's use the same voltage, so it does vary. I believe the Duron should do a voltage of 1.65V. 2.2V will fry it unless you have something like watercooling or liquid nitrogen on it.
CPU voltage on the K6's seem to be 2.4 and 2.3, for the 450 and 550 respectively.

The I/O voltage should be left alone or at the default setting. For the K6's it looks like 3.3V. If you have the manuals for these motherboards, check them out as even the crappiest ones will show info on the voltage settings.

Overvolting a little is usually okay if you have decent cooling, but jack it up too much and you'll know the smell of a fried CPU.

http://support.octek.com.au/Downloads/Files/Manual/P1/MVP3AT-B.pdf

Page 14 is the layout (SW1 & SW2), then just after that it says "setting for processors".

There is no I/O voltage setting & a core voltage setting on the board. You have to make a choice on what voltage to send, do I set it for the core or the I/O?

It's for the core voltage.

well I tried setting it to the I/O first & now none of the chips are working, so I have no clue if I messed up the board or if none of these chips ever worked. I have 3 ADM K6-2 chips, you'd think one of them works. Perhaps I should just go down & have these tested.

Aight, thanks for the feedback, i appreciate it.

If you set it to 3.45V, you may have fried the CPU. From the info I looked at in the manual, it was for the CPU core voltage. 2.3-2.4V is for the CPU's. I'm not sure of tolerance limit for overvolting (depends on the cooler used), but I suspect that you may have fried it...especially if you smelled something burning...

I didn't smell anyhting burning but the thing is I have 3 AMD K6-2 chips, so I have no clue if the board is no good, if it's all 3 of the chips, or if it's all of it. This is someone elses stuff so I could have got it in a non-working state - that's what I'm trying to dertermine.