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Two different motherboards Socket 7 and 50MHz FSB speed. How to set?

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First post, by junak

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Hello
I have two MOBO socket 7 and according on this page
1 https://theretroweb.com/motherboards/s/pcchips-m590
2 https://theretroweb.com/motherboards/s/epox-pronix-ep-58vp3a

both of them have the option to set fsb 50 MHz.

but I don't see such an option in the instructions. The minimum is 60 MHz. Is this an error on the retro web site? or maybe someone knows how to set 50 MHz on these boards. sometimes there are special jumper combinations.
I have Pentium 75 MHz and i need fsb 50 MHz to run.

RETRO Soyo SY-5XA + Pentium 166MMX + 32 MB RAM + S3 Trio 3D 4 MB VRAM + ESS AudioDrive ES 1869F

MODERN MSI MPG Z690 EDGE WIFI DDR4 + I7 12700K (stock UV) + 48 GB RAM 3600 MHz DDR4 + RTX 4070 Ti 12 GB VRAM

Reply 1 of 2, by PD2JK

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Try some undocumented options

1. PCChips: plug and play, look in the BIOS for FSB speed. If there is no option, you could try the SetMul tool.
2. Epox: SW1 = 4, 5 en 6 Just try all combinations and see what happens.

SetMul - Multiplier control for VIA C3 / AMD K6+7+8 Mobile / Cyrix 5x86

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Reply 2 of 2, by dionb

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The bus speed is generated by the PLL chip. The FSB jumpers are wired to its input. On the EP-58VP3A it's in the upper right hand corner of the board, just to the right of the DIMM slots, above the cache ICs. On Theretroweb pic I can see it's a Winbond chip but not the exact part number. Look that up, check its datasheet and you'll know if it can do 50MHz and if so how to set the jumpers. Can't figure it out? Post the part number here, we should be able to help.

And yeah, on the M590 it should be set in the BIOS. Note that BIOS defaults may be higher, so you might need a CPU that can handle 66MHz FSB to be able to get into BIOS to set the 50MHz before you can get the P75 to work.

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