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gg1978
Joined: 31 Jul 2012
Posts: 1052
Location: Indiana, USA
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 Posted: Fri Aug 01, 2014 11:09 pm Post subject: Fun with Pentium Pro overclocking :) |
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Well it is possible to get a early '97 vintage SL22V PPro to run at 266MHz, at least somewhat stable enough to run Memtest86+. 
The motherboard VRM was getting a bit warm enough to be uncomfortable to touch, but not horribly burning hot, so probably safe for the mobo for short term use, or long term with a fan blasting air at the VRM. It takes 3.5V to do it, there aren't a lot of PPro motherboards that have the necessary VID override jumpers to set the Vcore to 3.5V, or they lack the jumper settings to get the multiplier to 4X. The Iwill P6AN has the required settings, as well as a 50MHz bus setting available. 3.5V should be safe for a PPro, at least if temps are kept in check, as there were factory overvolted PPro Sspecs that basically said to override the default Vid to 3.5V.
On a side note, a long time ago i made the mistake of trying to overclock a 1M cache PPro on an Intel VS440FX motherboard.. It ran fine, until i ran Prime95 on it, then the VRM MOSFET exploded into shrapnel.. Hence why i'm using a 256K cache chip to do this little experiment. I might try a 512K L2 PPro, but a 1M cache chip is probably asking too much. |
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CPUShack
Joined: 16 Jun 2003
Posts: 34259
Location: State of Jefferson, USA
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| Posted: Sat Aug 02, 2014 2:26 am Post subject: |
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some cooling on the VRM may even improve the stability too
a ppro at 266 is probably pretty dang fast
I wonder how that board would do at OC'd a PPRO OD?
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joekster
Joined: 12 May 2011
Posts: 100
Location: Palm Beach, Florida USA
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| Posted: Sat Aug 02, 2014 6:17 am Post subject: |
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I never was able to get any of my ppro's to run at 266mhz...
FYI, I would suspect that the 512k cache versions would be better since the sram was mfg at .35u rather than the .5u of the 256k cache. |
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gg1978
Joined: 31 Jul 2012
Posts: 1052
Location: Indiana, USA
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| Posted: Sat Aug 02, 2014 3:27 pm Post subject: |
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| CPUShack wrote: | some cooling on the VRM may even improve the stability too
a ppro at 266 is probably pretty dang fast
I wonder how that board would do at OC'd a PPRO OD? |
Probably what limits the PPro's performance most is the FPM/EDO RAM that they were equipped with.. That PPro at 266 isn't quite what i would call stable, though the cooling could be improved, it does at least POST and run memtest, though i doubt it would be amenable to running Prime95 stable.. 240MHz would be more realistic for that.
As for the PPro Overdrives, they have an internal 5X locked multiplier, so you'd top out at 350MHz for those on a Socket 8 platform, as the only PPro mobo that i know of that will run faster than 66M natively is the PR440FX, which has an undocumented 70MHz bus speed setting.
I have however run a PPro Overdrive on a Socket 8 to Slot 1 adapter, and i think 450MHz was about the top end for the Overdrive at 90 X 5 on an Asus P3V4X.. I don't think it could do 100Mhz, though i could certainly try that out again as I do have a P3V4X in my slot 1 mobo collection.
If you run memtest86 on a PPro on Slot 1, the memory bandwidth goes way up, compared to FPM/EDO. I think it was PPro's hate of 16 bit code that resulted in the respin/rearchitecture that is the Pentium II..
I do have a late model SL22Z as well as a SY013 i had designated for this project as well, i just haven't run them to see whether they likes 266 as well. I doubt the SY013 will run much faster than 210 or so, as that was the first 200MHz model. |
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H3nrik V!
Joined: 15 Apr 2014
Posts: 1246
Location: Denmark
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| Posted: Sat Aug 02, 2014 4:06 pm Post subject: |
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| CPUShack wrote: | some cooling on the VRM may even improve the stability too
a ppro at 266 is probably pretty dang fast
I wonder how that board would do at OC'd a PPRO OD? |
Doesn't the OD have its own VRM on-board, thus taking the VRM of the motherboard out of the equation? |
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gg1978
Joined: 31 Jul 2012
Posts: 1052
Location: Indiana, USA
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| Posted: Sat Aug 02, 2014 4:19 pm Post subject: |
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| H3nrik V! wrote: | | CPUShack wrote: | some cooling on the VRM may even improve the stability too
a ppro at 266 is probably pretty dang fast
I wonder how that board would do at OC'd a PPRO OD? |
Doesn't the OD have its own VRM on-board, thus taking the VRM of the motherboard out of the equation? |
The PPro Overdrive asks for 2.5V via its VID pins.. Then there is a regulator on the Overdrive that knocks that down to 2.0V for the CPU core.. The 2.5V is for the L2 cache SRAM.. |
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Atom Ant
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| Posted: Sun Sep 09, 2018 2:07 am Post subject: |
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Hy,
It would be great to read further your overclocking experiment with Pentium Pro in that Pentium II Asus motherboard. |
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max1024
Joined: 15 Jan 2015
Posts: 636
Location: Belarus
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| Posted: Mon Sep 10, 2018 12:53 am Post subject: |
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Pentium Pro and socket8 is this is the most cheerful kind of overclocking. In the near future I'm just planning to do it again  |
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alvaro84
Joined: 17 Apr 2015
Posts: 80
Location: Fehérvárcsurgó, Hungary
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| Posted: Mon Sep 10, 2018 11:36 am Post subject: |
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| joekster wrote: | I never was able to get any of my ppro's to run at 266mhz...
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I played a bit with my 200/256s lately (I don't have any non-256k PPros but I'd definitely like to have at least one 512k and one 1M...). At least half of them was clearly unstable at 233MHz at stock voltage. And I can't tell now if the rest were stable, I just fooled around with DOS demos on the 440FX boards here (an Asus P6NP5 and a DTK). |
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max1024
Joined: 15 Jan 2015
Posts: 636
Location: Belarus
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| Posted: Mon Sep 10, 2018 1:04 pm Post subject: |
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I have overclock many PPro, some of them on FSB >100Mhz, some more then >300Mhz
But I hope is all interesting is ahead.
| alvaro84 wrote: | | joekster wrote: | I never was able to get any of my ppro's to run at 266mhz...
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I played a bit with my 200/256s lately (I don't have any non-256k PPros but I'd definitely like to have at least one 512k and one 1M...). At least half of them was clearly unstable at 233MHz at stock voltage. And I can't tell now if the rest were stable, I just fooled around with DOS demos on the 440FX boards here (an Asus P6NP5 and a DTK). |
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Atom Ant
Joined: 15 Sep 2018
Posts: 1
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| Posted: Sat Sep 15, 2018 5:02 am Post subject: |
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| max1024 wrote: | I have overclock many PPro, some of them on FSB >100Mhz, some more then >300Mhz
But I hope is all interesting is ahead.
| alvaro84 wrote: | | joekster wrote: | I never was able to get any of my ppro's to run at 266mhz...
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I played a bit with my 200/256s lately (I don't have any non-256k PPros but I'd definitely like to have at least one 512k and one 1M...). At least half of them was clearly unstable at 233MHz at stock voltage. And I can't tell now if the rest were stable, I just fooled around with DOS demos on the 440FX boards here (an Asus P6NP5 and a DTK). |
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Wonderful overclocking! But how the heck you do 100MHz FSB overclocking? In what kind of motherboard?
I'm just building my PPro system with Intel PR440FX, I cannot wait also to do some overclocking. Max 70MHz bus speed possible and multiplier adjustments... |
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max1024
Joined: 15 Jan 2015
Posts: 636
Location: Belarus
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| Posted: Sat Sep 15, 2018 11:59 am Post subject: |
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| 100 Mhz or more (S-8 limit is 75Mhz) is possible only via S8->Slot1 adapter. |
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ph4nt0m
Joined: 01 Jan 2018
Posts: 812
Location: Europe
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| Posted: Fri Oct 12, 2018 2:52 pm Post subject: |
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Once upon a time, I gave all my 200MHz PPro's a run @ 266MHz. I had a dozen of 256K, 4 512K and 6 1M. I kept the voltage at the default 3.3V for a reason. One 256K could pass Memtest86+ and another 256K hanged up in the process. The other 10 were unable even to start it. Two 512K hanged up in the process, the other two didn't even make to it. None of the 1M could even POST.
| CPUShack wrote: |
a ppro at 266 is probably pretty dang fast
I wonder how that board would do at OC'd a PPRO OD? |
PIIOD isn't overclockable. The multiplier is locked and almost all Socket 8 mainboards are limited to 66MHz FSB. Although I managed to overclock mine a long time ago by replacing the primary 14.318MHz crystal with a 16.000MHz one. It was stable, but there were side effects of such a crystal swap. |
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max1024
Joined: 15 Jan 2015
Posts: 636
Location: Belarus
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| Posted: Sat Oct 13, 2018 1:18 am Post subject: |
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| ph4nt0m wrote: |
PIIOD isn't overclockable. |
It is g00d overclockable on air possible to get 500Mhz  on liquid cooling even 600 |
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ph4nt0m
Joined: 01 Jan 2018
Posts: 812
Location: Europe
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| Posted: Sat Oct 13, 2018 6:38 am Post subject: |
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| max1024 wrote: | | ph4nt0m wrote: |
PIIOD isn't overclockable. |
It is g00d overclockable on air possible to get 500Mhz on liquid cooling even 600 |
I'm not talking about Slotket adaptors which allow to run it at the 100MHz FSB. The core is Deschutes which is known to do 500MHz. People bought PIIOD's with an intention to upgrade their Socket 8 based mainboards. No overclocking there. |
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