VOGONS


First post, by AlessandroB

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I was about to buy a system (IBM 300GL) which is originally configured with a PII350 (100x3.5) and I was thinking of installing a PentiumIII600 (the fastest slot1 at 2.0V). On the chassis at most it says that it works with PentiumII 450 (because I guess they are the fastest out). But if I install a PentiumIII 600 (it seems to me that I have already installed a PentiumIII on this generation of computers and there shouldn't be any difference between installing a PentiumII or III), the 6x multiplier, even if the mainboard doesn't support it, is blocked by the cpu, would it work the same?

Reply 2 of 10, by dionb

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Depends largely on BIOS and to a lesser degree on the VRM.

A P3-600 uses different CPUID and microcode than a P2. If BIOS fully supports it, it's fine. If not, the question is what BIOS does with an unknown CPU. Some just say 'unknown CPU' but boot on happily. Others refuse to boot... I'm not aware of 300GL behaviour.

The VRM is more subtle. The board is designed for a certain amount of current. A P2-450 has a TDP of 27.1W, so draws 13.55A at 2V. A P3-600 Katmai burns 34.5W, which draws 17.25A, so 27% more. Drawing that much more could be too much for the VRM, leading to voltage sags (causing instability) and/or damage to the VRM (worst case: it might fail catastrophically at some time). Or not... to be sure you'd have to check the regulator circuit and components.

Reply 3 of 10, by AlessandroB

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dionb wrote on 2023-01-25, 23:29:

Depends largely on BIOS and to a lesser degree on the VRM.

A P3-600 uses different CPUID and microcode than a P2. If BIOS fully supports it, it's fine. If not, the question is what BIOS does with an unknown CPU. Some just say 'unknown CPU' but boot on happily. Others refuse to boot... I'm not aware of 300GL behaviour.

The VRM is more subtle. The board is designed for a certain amount of current. A P2-450 has a TDP of 27.1W, so draws 13.55A at 2V. A P3-600 Katmai burns 34.5W, which draws 17.25A, so 27% more. Drawing that much more could be too much for the VRM, leading to voltage sags (causing instability) and/or damage to the VRM (worst case: it might fail catastrophically at some time). Or not... to be sure you'd have to check the regulator circuit and components.

IBM make a very good computer, i have a P75 that run a 233MMX without problem and without burning components. i think the big match will be the BIOS.

Reply 4 of 10, by PC Hoarder Patrol

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AlessandroB wrote on 2023-01-25, 23:56:
dionb wrote on 2023-01-25, 23:29:

Depends largely on BIOS and to a lesser degree on the VRM.

A P3-600 uses different CPUID and microcode than a P2. If BIOS fully supports it, it's fine. If not, the question is what BIOS does with an unknown CPU. Some just say 'unknown CPU' but boot on happily. Others refuse to boot... I'm not aware of 300GL behaviour.

The VRM is more subtle. The board is designed for a certain amount of current. A P2-450 has a TDP of 27.1W, so draws 13.55A at 2V. A P3-600 Katmai burns 34.5W, which draws 17.25A, so 27% more. Drawing that much more could be too much for the VRM, leading to voltage sags (causing instability) and/or damage to the VRM (worst case: it might fail catastrophically at some time). Or not... to be sure you'd have to check the regulator circuit and components.

IBM make a very good computer, i have a P75 that run a 233MMX without problem and without burning components. i think the big match will be the BIOS.

Pentium III 600 MHz (Katmai) support was added in BIOS version PDKT26A/PDJT26A...latest version is PDKT28A/PDJT28A which you can download from http://greyghost.mooo.com/pccbbs/commercial_desktop/

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pdjt28a.txt
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Reply 6 of 10, by Repo Man11

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Funny memory: My great uncle had an old OEM system with a P2, and a slightly less old Pentium 3 system with an Abit motherboard with failing capacitors. He had already moved to a replacement Socket A system, but I decided to reinstall Windows 98 for him on the P2 system so he would have a spare computer (this was late fall of 2002). I decided to try the P3 600 in the P2 system - it worked, but it didn't recognize the CPU properly. I hoped that it would recognize the CPU if I did a BIOS update, so after much searching, I found one. I think this was a Gateway computer, and the BIOS update was a Windows executable that gave you no options for saving the old BIOS or anything like that. After I did the update, the boot menu informed me that an unsupported CPU was installed and it halted. There was no way to go back to the old BIOS, no previous BIOS was anywhere to be found on the web, so I had no choice but to put the P2 back in.

"We do these things not because they are easy, but because we thought they would be easy."

Reply 7 of 10, by Paadam

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I had this type of 300GL back in 2004 iirc, got threee of them for real cheap and I even put Tualatin on it using Powerleap adapter. One of them worked out of the box with Coppermine also (100 MHz variant) as it had updated VRM.

Many 3Dfx and Pentium III-S stuff.
My amibay FS thread: www.amibay.com/showthread.php?88030-Man ... -370-dual)

Reply 8 of 10, by AlessandroB

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Paadam wrote on 2023-01-27, 05:27:

I had this type of 300GL back in 2004 iirc, got threee of them for real cheap and I even put Tualatin on it using Powerleap adapter. One of them worked out of the box with Coppermine also (100 MHz variant) as it had updated VRM.

i not understand why “one” work out of the box with tualatin, you have had 3 similar system and not identical?

Reply 10 of 10, by Paadam

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They all had same type (=identical numbers) but one of them had later production date by few months and had Coppermine capable VRM. Officially none of them supported Coppermines.
But all of them can work with Coppermine, just have to supply 1.8v to CPU (easiest using slocket+370 CPU).

Many 3Dfx and Pentium III-S stuff.
My amibay FS thread: www.amibay.com/showthread.php?88030-Man ... -370-dual)