VOGONS


First post, by Mourales

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Hello everyone!

I’ve just bought a Super Socket 7 motherboard and, at the moment, the only CPU I have available to test it is a Pentium 150.

According to the manual, the board supports Pentium CPUs with bus speeds from 66 MHz to 100 MHz. My question is: since the Pentium 150 uses a 60 MHz bus (if I’m not mistaken), can I still use it to test the motherboard?

I’ve attached an image of the jumper configuration from the manual.

Many thanks in advance for your help!

Reply 1 of 9, by Matth79

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Pin down the model, I'm sure the FS0/FS1/FS2 provide selections of bus clock, ah, SS7, so it might go up, but not down, but with 8 possible settings, there should be room for a wide range

Reply 2 of 9, by Mourales

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Matth79 wrote on 2026-06-22, 18:06:

Pin down the model, I'm sure the FS0/FS1/FS2 provide selections of bus clock, ah, SS7, so it might go up, but not down, but with 8 possible settings, there should be room for a wide range

Hello again and many thanks!

Te motherboard is a Biostar M5SAA.

https://theretroweb.com/motherboards/s/biostar-m5saa

Reply 3 of 9, by cyclone3d

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The BF jumpers are multiplier jumpers. The FSO are fsb settings.

The longer chip next to the FSO jumpers looks like it would be the clockgen chip. You should be able to look up the datasheet for that chip and it will tell you exactly what it supports.

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Reply 4 of 9, by BitWrangler

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150 should do 166 pretty easy, just don't run it like that on a stock sink for more than 30 years straight or your chance of failure may quadruple from 0.5% to 2%.

Unicorn herding operations are proceeding, but all the totes of hens teeth and barrels of rocking horse poop give them plenty of hiding spots.

Reply 5 of 9, by Mourales

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Thanks a lot!

Reply 6 of 9, by dionb

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If in doubt set for 2.0x 66MHz = 133MHz. That will give almost identical performance to 2.5x 60 = 150MHz as on So7 almost everything runs at bus speed, so higher bus is far more impacting than higher multiplier.

The manual is a classic example of far too much information about stuff that doesn't matter (pages on pinouts of standard interfaces) and excessively specific stuff for individual CPU types without just telling you what each jumper setting actually does like they did do with voltage setttings - there's a partial list at 1.6.3, but it's clearly not complete. There are three FSB jumbers, FS0, FS1 and FS2 and one SD. That gives 2^4=8 possible settings. I can't read the PLL chip markings (little black IC beyond FS0/1/2 and SD jumpers and the clock crystal), if you could, you can look up its datasheet and see what's what. Come to think of it, that silkscreen might show what you need. Maybe take a good pic of that area so both silkscreen settings and the PLL chip next to them are legible.

What we do see in 1.6.3 looks odd to me, it strongly looks like SD does more than just sync/async RAM - take a look at 66MHZ vs 90MHz, they have FS0/1/2 identical and only differ on SD off/on.

It is entirely possible that no speeds under 66MHz are available. I've found a picture of the similar Biostar M5SAF that's good enough to read its PLL. It's an ICS 9248-81. Looking at its datasheet it could well be what is used on the M5SAA too. Page 4 shows the available settings. You need to reed them back to front and inverted (i.e. they list SD first and FS0 last, and 0 = jumper on and 1= jumper off). The settings that match with 1.6.3 in the manual seem to correspond, in which case this is what you can choose from.

You can try and have some fun if you have PC100 or better RAM - the CPU might run at 1.5x 100MHz (FS0 on, FS1 on, FS2 off, SD off - and then BF0 open, BF1 open), or you could run it at 2.0x 66MHz but with RAM at 100MHz (FS0 off, FS1 on, FS2 on, SD on)

Reply 7 of 9, by Matth79

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Looks like the only undocumented ones are even higher, and not sure if an x2.5 P150 will honour an x2 selection as 133, or it might hold together at 166 if it remains at 2.5x

Reply 8 of 9, by dionb

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Matth79 wrote on 2026-06-23, 17:22:

Looks like the only undocumented ones are even higher, and not sure if an x2.5 P150 will honour an x2 selection as 133, or it might hold together at 166 if it remains at 2.5x

Apart from SY022 P133 CPUs, few early Pentiums had multiplier locks, so I expect that shouldn't be a problem. As for 166MHz, it most likely will. P150 CPUs were all cC0-stepping P54CS chips. That stepping had good yields and went all the way up to 200MHz. Why do you think Intel felt the need to lock the P133 CPUs with that stepping? 😉 - they will almost certainly run stable at 166MHz, probably permanently.

The level of over-engineering in the mid 1990s would be incomprehensible today. Little anecdote: I have a P233MMX on my desk at work as a memento. It was pulled from a failed server around 2018. It had probably been installed 20 years earlier and all that time it had run without any issues. Why had it failed? Because the heatsink had fallen off. During installation. That CPU had run with no heatsink for 20 years. The originally black OPGA package had been baked reddish brown. Yet it had still survived 20 years in production. I have no qualms whatsoever to run a CPU from that era 10% above stock with a heatsink firmly attached.

Reply 9 of 9, by Mourales

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Thanks so much, everyone! I managed to get it up and running, and it's working perfectly. THANK YOU, COMMUNITY! 😄