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486 CPU issue

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First post, by Stonker99

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Oh I remember the pain... I thought I’d upgrade my 486 from a DX2/50 to a DX2/66 I had lying around. I changed the jumpers as shown below, but for some reason my bios is showing it as a DX4/100 which the PC doesn’t even support! It runs but won’t boot. Not only that but it won’t even turn on with the original CPU in, and set back to 50 MHz. Any suggestions? Thanks!

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Reply 2 of 5, by SW-SSG

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DX2 chips are clock-doubled. The "CPU SPEED SELECTION" in that manual actually refers to the bus speed. For your DX2-50, use 25MHz. For your DX2-66, use 33MHz.

EDIT: *facepalm... looks like I missed something crucial. Sorry about that.

Last edited by SW-SSG on 2018-06-08, 23:44. Edited 1 time in total.

Reply 3 of 5, by Stonker99

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Thanks for the advice 😀 On this occasion however I think I did it right. The 33 and 66Mhz both use the same jumper settings 😀

Reply 4 of 5, by BeginnerGuy

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Stonker99 wrote:

Thanks for the advice 😀 On this occasion however I think I did it right. The 33 and 66Mhz both use the same jumper settings 😀

You're right! Hmm

Using the link above the only other CPU related jumpers I see are J11-J12, Are pins 1 and 2 closed on both of those (http://stason.org/TULARC/pc/motherboards/D/DI … -LPV-DECPC.html using this link) to indicate a 486dx/dx2?

I don't know much about those ST 486 chips (in case the CPU is the culprit) aside from that I believe they were 5V chips. I don't see any Voltage jumpers so I'm assuming that board is running 5V.

Sup. I like computers. Are you a computer?

Reply 5 of 5, by Stonker99

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Yeah I decided it's probably something related to it not being an Intel. There might be an updated BIOS for it around somewhere, but I don't think it's worth trying that. I might just get hold of an Intel 2/66 if I see one around 😀 Thanks again