Motherboard jumpers and CPU support \ VOGONS

Motherboard jumpers and CPU support

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First post, by FXing Serious

Posted on 2025-02-05, 09:28

FXing Serious Offline

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Hello,

I would like to know if I am able to upgrade the K6-2 that came with my NEC PC to a K6-2 550 AGR. The motherboard in question is a Biostar M5SAA. The manual has jumper settings for the multiplier for up to 450 mhz AMD K6-2/III CPU. I can set the jumpers by following the manual, but I don't really know what they do to really do something outside of what the manual states. Can someone help? I have attached an image of what I am interpreting by looking at similar jumper settings... Is installing an unsupported CPU something that can be done in these older motherboards? Thanks!

Last edited by FXing Serious on 2025-02-05, 12:17. Edited 1 time in total.

Reply 1 of 4, by dominusprog

Posted on 2025-02-05, 12:28

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It seems that JP4 (Fs1/FS2/SD) setes the external clock and JP2/JP4 (FS0) sets the multiplier.

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Reply 2 of 4, by dionb

Posted on 2025-02-05, 12:48

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dominusprog wrote on 2025-02-05, 12:28:

It seems that JP4 (Fs1/FS2/SD) setes the external clock and JP2/JP4 (FS0) sets the multiplier.

Don't think so. BF0/1/2 are the names of the multiplier pins on So7 CPUs, they do the multiplier. If you check the rows for the same multiplier these three pins always are the same. So BF0 open BF1 open BF2 close is 5.5x

FS sounds suspiciously like FSB. Here again the entries for same FSB give same result, so for 100MHz you want FS0 close FS1 close FS2 open

So if it's now set for 333MHz i.e. 5.5x66MHz, you only need to change FS2 from close to open to set it for 550MHz.

Reply 3 of 4, by Chkcpu

Posted on 2025-02-05, 13:09

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Hi FXing Serious,

This Biostar M5SAA board is very well suited for a K6-2/550 CPU, and you already found the 100MHz FSB and x5.5 multiplier setting combination for this CPU.

However viewing the tables from the manual you posted, I need to correct your interpretation.
The Bus and SDRAM clocks are set by the 4 jumpers JP4, not 3. So 100MHz CPU Bus and SDRAM clocks are set with FS0-FS1-FS2-SD: CLOSE-CLOSE-OPEN-OPEN.
The CPU multiplier is set by the 3 jumpers JP2, not 4. So for the K6-2/III CPU the x5.5 multiplier is set with BF0-BF1-BF2: OPEN-OPEN-CLOSE.

Note that your K6-2/550 AGR is a 2.3V part, but this Vcore setting is documented in the manual at page 1-25.

If you want to go further with the CPU upgrade, this board also supports the 2.0V K6-2+/III+ CPUs. The latest SAA0727F (07/27/200) BIOS fully supports these CPU models. When set to 2.1V Vcore, these K6plus models often reach a 600MHz overclock without problems!

Cheers, Jan

CPU Identification utility
The Unofficial K6-2+ / K6-III+ page

Reply 4 of 4, by FXing Serious

Posted on 2025-02-05, 13:44

FXing Serious Offline

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Chkcpu wrote on 2025-02-05, 13:09:
Hi FXing Serious, […]
Show full quote

Hi FXing Serious,

This Biostar M5SAA board is very well suited for a K6-2/550 CPU, and you already found the 100MHz FSB and x5.5 multiplier setting combination for this CPU.

However viewing the tables from the manual you posted, I need to correct your interpretation.
The Bus and SDRAM clocks are set by the 4 jumpers JP4, not 3. So 100MHz CPU Bus and SDRAM clocks are set with FS0-FS1-FS2-SD: CLOSE-CLOSE-OPEN-OPEN.
The CPU multiplier is set by the 3 jumpers JP2, not 4. So for the K6-2/III CPU the x5.5 multiplier is set with BF0-BF1-BF2: OPEN-OPEN-CLOSE.

Note that your K6-2/550 AGR is a 2.3V part, but this Vcore setting is documented in the manual at page 1-25.

If you want to go further with the CPU upgrade, this board also supports the 2.0V K6-2+/III+ CPUs. The latest SAA0727F (07/27/200) BIOS fully supports these CPU models. When set to 2.1V Vcore, these K6plus models often reach a 600MHz overclock without problems!

Cheers, Jan

Hello Jan! This is great info! Thank you for mentioning this because I had absolutely no idea. I will have a look at the other 2.0V K6-2+/III+ CPUs you mentioned. Thanks again! Appreciate it. =)

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