Why 5x86 P75 not start immediately??? \ VOGONS

Why 5x86 P75 not start immediately???

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First post, by AlessandroB

Posted on 2019-09-18, 23:21

AlessandroB Offline

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I have recently this configuration and I realized that after using it (even for a short time) if I turn off the computer with the bus set to 40mhz (160Mhz the CPU) the computer does not start, the monitor does not turn on. If immediately set the bus to 33Mhz (133Mhz the CPU) it starts immediately. If I leave the computer off for a while (about 30 minutes) then it restarts at 160Mhz. I checked and the CPU does not seem warm at all (mounted on top there is a heat sink + fan).
why? is like someting need to be discharge...

Reply 1 of 3, by SSTV2

Posted on 2019-09-18, 23:59

SSTV2 Offline

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Had the exact issue with my newly acquired Am5x86, but instead of 160MHz, I was trying to OC it to 180MHz. It would POST @ 180MHz only if the CPU was cold, after warming up, not even voltage bump to 5V could make MB POST with it. Your CPU probably gets unstable above 150MHz at default voltage or maybe it's undervolted.

Reply 2 of 3, by treeman

Posted on 2019-09-19, 01:01

treeman Offline

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I had the exact results on one of my 5x86 trying to run at 160 most over clock fine to 160 but not all

Reply 3 of 3, by AlessandroB

Posted on 2019-09-19, 08:56

AlessandroB Offline

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Rank: Oldbie
Posts: 1184
Joined: 2018-09-11, 19:17

I have discover something....

My mainboard in the jumper settings show me to set the 5x86 P75 at 3,3V but on the cpu i have discover that is indicate 3,45V. After setting the cpu at 3,45v instead 3,3 the system boot. It is under stress test now to confirm this hypothesis...

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