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Shuttle HOT-419 and am5x86-p75 (133 mhz)

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First post, by troydm

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Hi all, have this Shuttle HOT-419 motherboard with R2.0 bios 07/25/94 date
https://theretroweb.com/motherboards/s/shuttle-hot-419
set all jumpers and cpu voltage according to the manual, but no matter what I do cpu reports 100mhz on post screen instead of 133mhz
cpu voltage: 3.45v
bus ratio: 2x
bus speed: 33mhz
all other jumpers set for am5x86-p75

any suggestions? should I update bios to 419AIP06 version? also not sure how to do it, is bios chip rewriteable or not

Reply 1 of 2, by majestyk

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The BIOS chip is rewritable, but since it´s an EPROM you will need to erase it with a UV-eraser first.
Even BIOS 06 is from 1994, so it´s probably not aware of any 5x86 @ 133 MHz and will report a 486 @ 100 MHz instead. This is a cosmetic issue as long as the CPU is running at the correct speed.

Reply 2 of 2, by troydm

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seems like it, I did benchmarks and speed is consistent with 133mhz amd cpu, also hwinfo tool reports it as 486 running at 133mhz (4x33mhz) , only thing which is not working now is a turbo button, so system only works and boots when turbo switch is on, when it is off motherboard won't even show post codes, and if I turn it off when system is running it just freezes. not sure if it's even worth trying to upgrade the bios. I'll try ordering some W27c010-70 bios chips from Aliexpress and flashing it with different version of bios later I guess

note: turbo switch works fine with amd dx4 100mhz cpu on this motherboard in 3x33mhz mode

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