Cannot overclock a PMMX 166 \ VOGONS

Cannot overclock a PMMX 166

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First post, by vladstamate

Posted on 2017-01-12, 00:12

vladstamate Offline

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Hi all,

I have a Pentium MMX 166Mhz on a P55XB2 Iwill motherboard of which I found the manual here.

Now, no matter what I do I cannot seem to make it run at anything above 188Mhz. I want to try 200Mhz. I tried the jumpers on the website (and many other combinations I thought of) and I either get 188 or something lower (166, 150, 133, 120, etc). Is it possible at all to achieve that given the processor and the motherboard I have?

I have also try moving the jumper for the voltage from Auto to either 3.1V or 3.2V and that did not have any impact.

Any suggestions?

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Reply 1 of 8, by Kamerat

Posted on 2017-01-12, 00:17

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I guess the limitation is your motherboard and/or RAM, that it can't handle more than 75MHz FSB and your CPUs maximum multiplier is 2,5.

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Reply 2 of 8, by Imperious

Posted on 2017-01-12, 00:23

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An MMX cpu is dual voltage and should be set to 2.8v.
As Kamerat said, likely it is multiplier locked so 188mhz is as good as it gets.

I would suggest getting hold of a 200mmx or 233mmx cpu.

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Reply 3 of 8, by vladstamate

Posted on 2017-01-12, 00:44

vladstamate Offline

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Thank you both, spot on. I have a Pentium MMX 166 SL27H which according to this thread, it either does 2.0 or 2.5.

I am getting a 233Mhz one now.

Reply 4 of 8, by kanecvr

Posted on 2017-01-12, 16:24

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pentium MMX CPUs should not be multiplier locked. I've never seen a multi-locked pentium CPU. Ever - and I have about - 20-30 in my collection...

Reply 5 of 8, by candle_86

Posted on 2017-01-12, 16:45

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Intel started locking the MMX chips espcially the 166 because everyone would buy the 166 and set it to 3.5 and save a but load of cash

Reply 6 of 8, by Tetrium

Posted on 2017-01-12, 16:49

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kanecvr wrote:
pentium MMX CPUs should not be multiplier locked. I've never seen a multi-locked pentium CPU. Ever - and I have about - 20-30 in my collection...

I've once tested a large batch of MMX 200 and MMX 166 chips and many were in fact locked above the multiplier they were binned for. Too bad I lost my sheet of paper I had used to write down statistical data when I ran these tests.

Iirc MMX 233 chips seemed to not be affected in any way what CPU multipliers are concerned and had all 4 multipliers available.

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Reply 7 of 8, by meljor

Posted on 2017-01-12, 20:53

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kanecvr wrote:
pentium MMX CPUs should not be multiplier locked. I've never seen a multi-locked pentium CPU. Ever - and I have about - 20-30 in my collection...

Yep, they can be locked. I have 5 x 200mmx cpu's, three are locked (can go down but not up to 3,5 multi) and two of them i can select 3,5x multi and also go down. (3,5x is intel max multi on desktop mmx).

I believe the late mmx cpu's are locked, early ones are not.

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Reply 8 of 8, by kanecvr

Posted on 2017-01-13, 02:51

kanecvr Offline

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Tetrium wrote:
kanecvr wrote:
pentium MMX CPUs should not be multiplier locked. I've never seen a multi-locked pentium CPU. Ever - and I have about - 20-30 in my collection...

I've once tested a large batch of MMX 200 and MMX 166 chips and many were in fact locked above the multiplier they were binned for. Too bad I lost my sheet of paper I had used to write down statistical data when I ran these tests.

Iirc MMX 233 chips seemed to not be affected in any way what CPU multipliers are concerned and had all 4 multipliers available.

Just tested all the 166 mhz pentiums I had on hand (4 non-mmx 166Mhz pentiums, as well as the 2 ceramic pentium 166 MMX and one organic package 166Mhz MMX) none are multiplier locked (they will all post at 200 MHz) - but apparently I have a 200MHz pentium MMX witch is... (organic package). Thinking back I think I did encounter a multi-locked pentium MMX - a friend of mine back in the day (2000?) got a hand-me-down PC from a relative, and I tried to OC it to 200Mhz to squeeze a bit more umph out of it - to no avail. Regardless of choosing 3x or 3.5x, it would consistently post at 166MHz, but I blamed it on the motherboard. Oddly enough it ran fine with a 400Mhz K6-2 at 66MHz / 6x(2x). I don't remember what board he had (possibly a lucky star board - those were popular here) but it was based on the VIA VP3 chipset.

Huh - all that swapping out socket 7 pentiums and messing with jumpers must have jogged my memory...

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