It depends of the way your motherboard is made.
Some boards let you use the voltages below 3.3V, others don't. Boards with automatic settings exist but they're rare and I doubt any OEM have done this.

Socket 7 has *optional* dual voltage planes, the fundamental required difference between So5 and So7 is the presence of the BF1 pin for 2.5x and 3x multipliers. So a lot of early So7 boards do not offer split voltage, only that extra multiplier to be able to use P54C CPUs above 133MHz.

And as for the "different socket", the socket itself is completely identical, it's just different wiring for at least one of th pins, that's all.

Voltage settings on So7 are typically done via jumper or dipswitch, there's no autodetect logic or voltage identifiers in the CPU.

Can you post pics and or the exact model number of the motherboard?

Olivetti motherboard https://imgur.com/gallery/hLL4G8h

Olivetti BA2306 is the model number
https://imgur.com/gallery/vj9OmuA

There is a voltage regulator with a big heat sink at the bottom right, might that have something to do with it?

dionb wrote on 2021-01-30, 19:50:

And as for the "different socket", the socket itself is completely identical, it's just different wiring for at least one of th pins, that's all.

I believe this is true for the processor side, however the Socket 7 socket has an additional "KEY" position that is not present on Socket 5 sockets.
For referece I have included pictures of Socket 5 and Socket 7 with markings as well as the Pentium Processor Flexible Motherboard Design Guidelines (Appendix B / Pages 39-41).

Deksor wrote on 2021-01-30, 19:12:

It depends of the way your motherboard is made.
Some boards let you use the voltages below 3.3V, others don't. Boards with automatic settings exist but they're rare and I doubt any OEM have done this.

be careful with the auto setting there are quite a few reports out there of the board setting it incorrectly.

The voltage is super easy to check.

Re: Dual CPU Socket 5/7 Boards

dionb wrote on 2021-01-30, 19:50:

Socket 7 has *optional* dual voltage planes, the fundamental required difference between So5 and So7 is the presence of the BF1 pin for 2.5x and 3x multipliers. So a lot of early So7 boards do not offer split voltage, only that extra multiplier to be able to use P54C CPUs above 133MHz.

And as for the "different socket", the socket itself is completely identical, it's just different wiring for at least one of th pins, that's all.

Voltage settings on So7 are typically done via jumper or dipswitch, there's no autodetect logic or voltage identifiers in the CPU.

Check out other members replies above. Some good info in them.

Thanks. A diffinitive answer seems to be measuring the voltage, and it may be simple if you know how to use a multimeter (I don't), but can learn😁. That post measures between the chassis and the further most fet? presumably in my case that you'd be measuring between the chassis and a pin on the vrm, while running an mmx chip? to see if it knocks down to 2.8 or whatever for the chip. I've also found the vrm is a EZ1585CT and the spec docs are on the net (not that I really understand them) they suggest a range between 2.5 and 3.6v.

If I'm not mistaken you should have a transistor with large heatsink next to your CPU socket and between that and the outer edge of the board should be two rows of fifteen solder points, correct?
This is where an optional VRM module for split voltage support can be installed. If it's not present you should only have 3.3V (and maybe ~3.45V) avaliable.

OK cool thanks, I'll just stick a standard pentium 200 in

charliegolf wrote on 2021-01-31, 11:13:

Thanks. A diffinitive answer seems to be measuring the voltage, and it may be simple if you know how to use a multimeter (I don't), but can learn😁. That post measures between the chassis and the further most fet? presumably in my case that you'd be measuring between the chassis and a pin on the vrm, while running an mmx chip? to see if it knocks down to 2.8 or whatever for the chip. I've also found the vrm is a EZ1585CT and the spec docs are on the net (not that I really understand them) they suggest a range between 2.5 and 3.6v.

look at the pic closly. Usually there will be two fets one will be the one you are looking for. Do not short something while poking the probe in there only touch the big tab on the fet nothing else and have someone else hood the negative lead so it doesn’t fall and distract you

Best to test voltage with a high voltage chip installed. If you get the wrong setting you are more likely to be fine.

Btw that heatsink in all likelyhood is live with the voltage you are looking to measure. That pic linked above looks like a single voltage motherboard. One fet? If so prob gonna need a cpu upgrade interposer.

charliegolf wrote on 2021-01-31, 12:08:

OK cool thanks, I'll just stick a standard pentium 200 in

Awesome! It'll be a great DOS machine.👍😁

Dude wants way too much for it though 🤣 I got one the other day for 15$ max I’d say is 100$

I’m still looking for the k6III one from powerleap though

Another link

Socket 7 PowerLeap PL-K6-III (ultimate upgrade)

They seem crazy expensive. The reason I wanted to go faster was because I have a pci voodoo banshee and nowhere to put it, it's my only 3dfx card and wanted a glide machine. I'll use this olivetti for an early 3d machine and stick with a 200 and dos/win 95. I can probably build a pII or similar for less than what some people are asking for converters.

Please do not post ebay links