Overclocking AMD 5x86 to 180MHz \ VOGONS

Overclocking AMD 5x86 to 180MHz

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First post, by Anonymous Coward

Posted on 2014-11-25, 00:15

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How many people on here have successfully overclocked their 5x86 to 180MHz?

-Specifically which chip are you using?
-Is it completely stable?
-What voltage was required to get it stable?

I have a late model 16BGC with a 2000 date code. Although it is the best of my four 5x86 chips, it still does not go to 180MHz easily. I am using a board that can take crystal oscillators, so I am using a 45MHz bus. This has been proven to work well with a 5x86 at 133MHz (3x45).

My system seems to be stable in DOS playing games like DOOM and GTA1. However, NT4 freezes while loading the kernel. However, if I increase the voltage to 4V, I can get it to boot into NT for a few minutes before crashing.

Do you think it would be worth my time to push the voltage higher?

"Will the highways on the internets become more few?" -Gee Dubya
V'Ger XT|Upgraded AT|Ultimate 386|Super VL/EISA 486|SMP VL/EISA Pentium

Reply 1 of 9, by smeezekitty

Posted on 2014-11-25, 00:44

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I don't have a 5x86 but I seriously wouldn't go any higher than 4V. Maybe try 4V and see if you can cool it further?

Reply 2 of 9, by Anonymous Coward

Posted on 2014-11-25, 01:32

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I know Cyrix 5x86s are pretty easy to burn out at high voltages, but there are numerous reports of people running their AMD 5x86 chips at 5V for prolonged periods of time (sometimes years) with no ill effects.

"Will the highways on the internets become more few?" -Gee Dubya
V'Ger XT|Upgraded AT|Ultimate 386|Super VL/EISA 486|SMP VL/EISA Pentium

Reply 3 of 9, by smeezekitty

Posted on 2014-11-25, 04:19

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5V is 50% overvoltage compared to 3.3V. That is quite a bit.

I will let the more experienced members weight in but I don't think that it is a good idea

Reply 4 of 9, by noshutdown

Posted on 2014-11-25, 05:36

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amd datasheet lists the absolute vcc limit(that will cause damage) for the amd5x86 at 4.6v, so 5v is not really safe. unfortunately most 486 boards don't have many voltage options.

Reply 5 of 9, by Anonymous Coward

Posted on 2014-11-25, 05:53

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I have modified a VRM with a trim pot, so I can set the voltage to whatever I need.

"Will the highways on the internets become more few?" -Gee Dubya
V'Ger XT|Upgraded AT|Ultimate 386|Super VL/EISA 486|SMP VL/EISA Pentium

Reply 6 of 9, by feipoa

Posted on 2014-11-25, 07:02

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I recall user retrogames running an Am5x86-ADW at 5V, 200 MHz. He ran all the 486 benchmarks on my list without any problem. He did have a large Pentium 4-style heatsink/fan on it though.

Perhaps you could take it up to 4.5 V just to see if it buys you anything.

I would really like to know more about the few cases of users running at 180 MHz and sub-5V. User numeriK has an Am5x86-180 setup listed in his signature.

Plan your life wisely, you'll be dead before you know it.

Reply 7 of 9, by kixs

Posted on 2014-11-25, 07:29

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I run one AMD 486DX2-80, rated 3V at 5V without problems. 180MHz is another story, but the manufacturing process is the same (or is it?). So a huge heatsink is needed.

Requests are also possible... /msg kixs

Reply 8 of 9, by Jolaes76

Posted on 2014-11-25, 10:48

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Definitely...
I recall one of my 5x86 builds, Soyo SAW2 based AMD 5x86 ADZ (?) run pretty stable around 4V at 180Mhz, but I am sure any Windows would have crashed immediately. But I never wanted to run Windows on it. I just modded an Socket A copper cooler in the end for my peace of mind... But one needs more juice, prolly 4.5 -5V and water/nitro for a stable 200 mhz OC... AND luck with that:

http://bacsis-tuning.hu/2012/03/hetkoznapi-sz … s-egy-486-ossal

Last edited by Jolaes76 on 2014-11-26, 09:52. Edited 1 time in total.

"Ita in vita ut in lusu alae pessima iactura arte corrigenda est."

Reply 9 of 9, by Anonymous Coward

Posted on 2014-11-25, 14:20

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Turns out my VRM will need extra modification if I want voltages between 4 and 5V, so I'm probably going to back off. I don't want to feed this chip the full 5V. I might try to step it down to 172MHz to see what happens though.

"Will the highways on the internets become more few?" -Gee Dubya
V'Ger XT|Upgraded AT|Ultimate 386|Super VL/EISA 486|SMP VL/EISA Pentium

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