Ive googled and found that wikipedia lists one voltage and cpuwolrd lists two voltages.
Voltage vcc and voltage IO

Whats the deal then?!

Look at the back of your CPU, it will probably say something like '2.8v'. The I/O is still operating at 3.3V though, but except for overdrives, I don't think there are any MMX that operate at 3.3V

Grub3r wrote:

Hi all. […]
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Hi all.

I have a mb with p120 which I want to upgrade with p200mmx

As now the board is configured with single voltage jumpers.

Im unsure if the new cpu is single or double voltage.

Would you explain what the difference is.

P120: sy062, a80502120
P200mmx: sl27j, fv80503200

I can also see that the voltage was set to 2.8 for p120 which is wrong?

Thanks.

P120: single, 3.3V
P200MMX: dual, 2.8V
Setting P120 at 2.8V is wrong, but it also means your mobo supports dual plane CPUs.

Yep, different voltage for interface and core, 3.3 and 2.8V.

lazibayer wrote:

Setting P120 at 2.8V is wrong, but it also means your mobo supports dual plane CPUs.

Nice comment. I believe there weren't other socket 7 CPUs of that era operating at 2.8V? I really can't remember, just throwing this in for the sake of the discussion, but you're probably very correct with this observation.

Deksor wrote:

Look at the back of your CPU, it will probably say something like '2.8v'. The I/O is still operating at 3.3V though, but except for overdrives, I don't think there are any MMX that operate at 3.3V

Yepp, it does say 2.8

The question is why and how do I know if the cpu dual or single voltage.

As a rule, all P55C (e.g. Pentium MMX) chips are "dual-voltage" parts.

lazibayer wrote:

P120: single, 3.3V P200MMX: dual, 2.8V Setting P120 at 2.8V is wrong, but it also means your mobo supports dual plane CPUs. […]
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Grub3r wrote:

Hi all. […]
Show full quote

Hi all.

I have a mb with p120 which I want to upgrade with p200mmx

As now the board is configured with single voltage jumpers.

Im unsure if the new cpu is single or double voltage.

Would you explain what the difference is.

P120: sy062, a80502120
P200mmx: sl27j, fv80503200

I can also see that the voltage was set to 2.8 for p120 which is wrong?

Thanks.

P120: single, 3.3V
P200MMX: dual, 2.8V
Setting P120 at 2.8V is wrong, but it also means your mobo supports dual plane CPUs.

Okay but still not quite.
How do I know if the cpu is single ir dual voltage and what is the difference?

And what do you mean that the board is supoorting dual plane CPUs ?

The mb is "km-t5-t1" rev 1.32
Sorry, photos are too big to upload...

Found some info on duL voltage.

Still wonder what you ment by dual plane CPUs..

Grub3r wrote:

How do I know if the cpu is single ir dual voltage?

Google, Wikipedia, Intel's datasheet, ask vogoners, etc.

Grub3r wrote:

And what do you mean that the board is supoorting dual plane CPUs ?

Dual plane = dual plane voltage = dual voltage = dual split rail voltage = ...

lazibayer wrote:

Google, Wikipedia, Intel's datasheet, ask vogoners, etc. […]
Show full quote

Grub3r wrote:

How do I know if the cpu is single ir dual voltage?

Google, Wikipedia, Intel's datasheet, ask vogoners, etc.

Grub3r wrote:

And what do you mean that the board is supoorting dual plane CPUs ?

Dual plane = dual plane voltage = dual voltage = dual split rail voltage = ...

Cool. Thanks.
Intel says all MMX pentium 1s are dual.
Just got it working.
At first it didnt post but found manual and one of the jumpers which wasnt pictured on the mb had to be active ..

lazibayer wrote:

P120: single, 3.3V
P200MMX: dual, 2.8V
Setting P120 at 2.8V is wrong, but it also means your mobo supports dual plane CPUs.

Note that this doesn't matter - single-plane CPUs really only have one voltage plane, so Vcore is the same as Vio - so it doesn't matter what you set core voltage to, it will run on the I/O voltage (3.3V usually) anyway.