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Conputer only boots after a replug, help?

The computer boots fine if i unplug the mains then replug - it will then boot perfectly normal, once i turn it off tho it just refuses to turn on, doesnt get to post (screen stays black), so i have to unplug it again and it works fine... have tried different PSU's, CPU's and ram, out of ideas

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lemonie7 years ago
Me too. Is this the power-on button that just doesn't do anything, until after you unplug-plug? L
Cybot Rules (author)  lemonie7 years ago
To reply to you both, Thanks but ive pritty much figured it out - if its internal clock is running at anything higher the 100Mhz this happens, even tho the book says its perfectly fine at 248 Mhz....if i under clock it down to the 100Mhz it boots fine... any ideas why?
This would be the Front Side Bus speed?
Your CPU will be on a multiplier of the FSB clock, as will the RAM. I'd say you've over clocked one of these far too much. Check what you've got and what cranking the clock up to 248MHz works out at for both.

L
Cybot Rules (author)  lemonie7 years ago
Yeah, i think its the cpu clock, this cpu runs fine at 320 Mhz but i think its the mobo having problems... any ideas?
In BIOS - you'll be increasing the clock speed rather than the CPU multiplier? You're most likely increasing the RAM speed at the same time.
E.g. My CPU is running 12 x 200MHz (2.4GHz), the RAM is running 2 x 200MHz (400Mhz) off the same 200MHz clock.

Do you know: what the CPU will reliably run at (320Mhz makes it sound like an old Pentium?), what speed the memory will reliably run at, and what speed your FSB will run at?

L
Cybot Rules (author)  lemonie7 years ago
its a pentium 4 cpu, and it works perfectly at 320 in the old mobo, same ram from that mobo 2.... damm
But what is the RAM actually running at? 320 sounds a bit high for a P4 RAM, the RAM might only be good for 200MHz? L
Cybot Rules (author)  lemonie7 years ago
Maybe...
That's probably it. You may be able to up the CPU multiplier and leave the FSB at 200MHz (it works at 200?) L
MrThingys7 years ago
Internal power supply is probably faulty. Most are not all that well made to begin with. A leaky/faulty capacitor or diode is most likely the cause. It's probably cheaper to look for a replacement. Ebay is a good source for replacements depending on the computer. (Once you replace it, send me the old one so I can dissect it :) )