When an 486OD processor clocks higher than listed? \ VOGONS

When an 486OD processor clocks higher than listed?

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First post, by benjibarnicals

Posted on 2022-07-23, 09:24

benjibarnicals Offline

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Hey all,

I recently got hold of a working DX4ODP75. Which by all accounts from my checks is meant to be a DX4 clocked at 75Mhz. When I added this to my exsting 486 PC (It was originally running a DX2/66 chip, the motherboard only lists compatibility upto 50mhz. Anyway, the chip works fine, but when I run diag software like PC Check etc it recognises is as a DX4 but clocked at 100mhz. Is this normal? Is it running higher than it should do?

Certainly from a performance side its feels like a DX4/100, Windows 3.11 is a lot more snappy, processing WAVE/MOD etc music runs without an issue (where as I used to have stuttering trying to play MOD files using Ultimod on my DX2/66).

Whats your thoughts?

Ben

Reply 1 of 5, by rmay635703

Posted on 2022-07-23, 15:39

rmay635703 Offline

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If you put a dx4-75 in place of a dx2-66 it has to overclock to 100mhz or crash.

If you don’t want to overclock change the FSB to 25mhz

Back in the day it seems like a dx4-75 to 100 overclock was popular

Reply 2 of 5, by benjibarnicals

Posted on 2022-07-23, 17:12

benjibarnicals Offline

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Ahhh thank you,

Not sure I can change the FSB of the processor via the BIOS, unless there's a jumper on the CPU, if its not causing too much harm on the CPU i'll keep it as overclocked 😁

Reply 3 of 5, by majestyk

Posted on 2022-07-23, 17:30

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Make sure there´s sufficient cooling by adding a small fan.

Reply 4 of 5, by benjibarnicals

Posted on 2022-07-24, 20:04

benjibarnicals Offline

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Ok will see what I can do with that, and where (if any) header pins exist for a fan. Thank you.

Reply 5 of 5, by mkarcher

Posted on 2022-07-25, 15:49

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benjibarnicals wrote on 2022-07-23, 17:12:

Not sure I can change the FSB of the processor via the BIOS, unless there's a jumper on the CPU, if its not causing too much harm on the CPU i'll keep it as overclocked 😁

There most likely is a block of three or four jumpers on the mainboard to set the FSB. CPUs telling the mainboard the required FSB (so you might jumper something on the CPU) weren't a thing before Slot 1 (Pentium II). On 486 processors, you should set FSB, CLKMUL jumper (on non-overdrive DX4 only) and voltage (for low-voltage processors like non-overdrive DX4 or Am5x86) before you even power on the system. As long as your system doesn't crash at FSB33 (100 MHz), you can keep it the way you have it now.

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