VOGONS


First post, by mattrock1988

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I recently ordered a Tyan S1856S Tomahawk BX motherboard on eBay for a new build I'm working on. It's designed for Socket 370 CPUs and I have a Celeron 500 I'd like to install in it. In order to reach the rated speed on a 66 MHz FSB, it needs to be clocked to 7.5x.

However, the motherboard user guide only mentions up to a 7x multiplier, via jumpers on the mainboard. Is there any way to force this higher somehow? Or is this a hard limitation?

Retro PC: Intel Pentium III @ 1 GHz, Intel SE440BX-2, 32 GB IDE DOM, 384 MB SDRAM, DVD-ROM, 1.44 MB floppy, Nvidia GeForce 4 Ti 4600 AGP, Creative SoundBlaster AWE64 Gold, Aureal Vortex 2
I only rely on 86box these days. My Pentium 3 PC died. 🙁

Reply 1 of 4, by dionb

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Is your Celeron 500 an engineering sample?

If not, it has a fixed mulitplier and ignores whatever the board tells it, so if the motherboard supports Celeron Mendocino CPUs - which it does, in fact that's the only type it supports with its So370 PPGA socket - it will run fine at that speed.

Potential issues might be:
- an inability to deliver enough current to run the faster CPU, but this is unlikely on a solidly designed Tyan board (and it's not as if a C500 uses significantly more than an officially supported C466)
- no BIOS support for the specific stepping/model CPU. Unlikely, but worst-case there were multiple BIOS updates for it; if it refuses to boot with the C500, insert a C466 or lower and update BIOS, then most likely you can upgrade to the C500.

Reply 2 of 4, by mattrock1988

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Fantastic response. To wit, this CPU is not an engineering sample and is a retail one. I’ll definitely give it a go then. 😀

With that in mind, I do wonder why these jumpers exist on the motherboard in the first place then? Is it for overclocking?

Matt

Retro PC: Intel Pentium III @ 1 GHz, Intel SE440BX-2, 32 GB IDE DOM, 384 MB SDRAM, DVD-ROM, 1.44 MB floppy, Nvidia GeForce 4 Ti 4600 AGP, Creative SoundBlaster AWE64 Gold, Aureal Vortex 2
I only rely on 86box these days. My Pentium 3 PC died. 🙁

Reply 3 of 4, by dionb

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Not really as the CPU multiplier lock prevents that too. The only way to influence the speed of a Celeron Mendocino is through changing the FSB. The jumpers are there because Intel specified that the motherboard must be able to sent BF (multiplier) settings tot the CPU, even if retail CPUs ignore it. Their only actual use on an So370 board is for those unlocked engineering samples. On Slot 1 boards they do serve an actual purpose as early Pentium II CPUs weren't multiplier locked.

Reply 4 of 4, by mattrock1988

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Good to know. I appreciate the fast responses.

I did order an early Coppermine Pentium III (500E) as well just to hedge my bets, but I really want this to be a Celeron.

Retro PC: Intel Pentium III @ 1 GHz, Intel SE440BX-2, 32 GB IDE DOM, 384 MB SDRAM, DVD-ROM, 1.44 MB floppy, Nvidia GeForce 4 Ti 4600 AGP, Creative SoundBlaster AWE64 Gold, Aureal Vortex 2
I only rely on 86box these days. My Pentium 3 PC died. 🙁