5x86 undervolted? \ VOGONS

5x86 undervolted?

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First post, by cj_reha

Posted on 2017-09-13, 23:29

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Recently got an AMD 5x86-P75 (X5-133ADZ) for socket 3 and planning to use it in my socket 3 build. Small problem, it is marked 3.45 volts and the board only has options for 3.3volts. Board is PC Chips M912 rev. 1.7 with white ISA slots. Is it safe to run it slightly undervolted? Or will it not work? Or strain the VRM?

Thanks.

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Reply 1 of 6, by noshutdown

Posted on 2017-09-14, 00:22

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such small difference is negligible. for the datasheet, 3.45 is just the nominal voltage, while the working range is 3.3-3.6, so it should be fine.

Reply 2 of 6, by Anonymous Coward

Posted on 2017-09-14, 06:13

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It's also quite likely the motherboard does not produce the voltage claimed. It could be considerably lower or higher than the 3.3V indicated. Best to check with a multimeter. I suspect the actual voltage provided is closer to 3.45. Motherboard companies had a bad habit of putting all 3.xV chips under the "3V" or 3.3V umbrella.

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Reply 3 of 6, by cj_reha

Posted on 2017-09-14, 10:27

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Bad news: the board does not POST with the cpu installed. I have set all jumpers according to the manual, yet when I put a 486 dx4 in, it identified the cpu as that.

Tried the 5x86 in my AOpen VI15G, and after setting jumpers for "Misc 5x86" it identified it as a 100mhz dx4 as well.

This is weird, is it a mislabeled chip or something?

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Reply 4 of 6, by Deksor

Posted on 2017-09-14, 10:35

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Put the multiplier to 2x, the 5x86 will take it as a 4x multiplier. Some motherboard might need a bios update to work properly with a 5x86. My Acer/Aopen AP43 needed one. It POSTed with the 5x86, but it crashed after counting the ram. When set as a DX4 it worked flawlessly. After updating the bios, it worked flawlessly too

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Reply 5 of 6, by Anonymous Coward

Posted on 2017-09-14, 12:40

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M1sc is the Cyrix 5x86. Try using the settings for intelDX4 with writeback cache.

"Will the highways on the internets become more few?" -Gee Dubya
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Reply 6 of 6, by noshutdown

Posted on 2017-09-15, 11:11

noshutdown Offline

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can you guys post some photos of your aopen 486 boards?
i used to have a 486 board named "ahead pb4s", which i suspect to be made by aopen, so i want to see if they have anything similar in style.

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