# Presume CPU dead, how likely mobo is ok?

## drwook

ok so I had a PSU die, and replaced it.  Things were overheating, but after cleaning óut he cpu heatsink all seemed ok for a few days.

however, now it appears the CPU is probably dead.  But I was hoping some of you guys could confirm my thinking here & give a little advice on hether o euse the motherboard?

AM2+ asrock otherboard - nothing special I guess, geforce 8200 chipset.  4x2GB DDR2 RAM ád e 'probably dead' CPU was a Phenom II 920.

now, with only the ATX PSU connector connected, things seem to spin up.  but as soon as the 4 pin connector ís attached, it spins up literally for no more than 2 seconds.  I'm fairly certain the 4 pin connector just 'feeds' the CPU, ergo this means the CPU is dead - would everyone agree?

But.... if I need to buy a new CPU I can't go down, so may as well buy a 6-core.  But is it likely to be safe to re-use the motherboard, or is there any way (without a spare compatible CPU  :Sad:  ) to check it over?

issue being new mobo likely means going AM3 and replacing the RAM with DDR3 too....  which is going to start making this look more expensive than I'd like ít to.

I guess secondarily...  if I need a new mobo, is it worth considering buying another AM2+ board so I can e-use my RAM?  Guessing none of them support sata3/usb3 but could save me ~£150 on RAM.  any óther performance issues going 2+ rather an 3?

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## ssteinberg

 *drwook wrote:*   

> 
> 
> now, with only the ATX PSU connector connected, things seem to spin up.  but as soon as the 4 pin connector ís attached, it spins up literally for no more than 2 seconds.  I'm fairly certain the 4 pin connector just 'feeds' the CPU, ergo this means the CPU is dead - would everyone agree?

 

No, the motherboard controls voltage, nothing is fed directly. Check for busted capacitors, usually that is what fails first on cheap motherboards. Do try another PSU even if it is a new one, can be a faulty one.

 *drwook wrote:*   

> 
> 
> But.... if I need to buy a new CPU I can't go down, so may as well buy a 6-core.  But is it likely to be safe to re-use the motherboard, or is there any way (without a spare compatible CPU  ) to check it over?
> 
> 

 

You can't know for sure. CPUs usually don't just fail. Maybe it is fine, maybe it was damaged by the motherboard/PSU. If you can get your hands on a spare mobo you can test it, it is unlikely for the CPU to damage the motherboard. It isn't as safe the other-way around. I'd not want to buy a new CPU and stick it on a faulty motherboard.

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## NeddySeagoon

drwook,

The 4 pin connector (+12v)  feeds the Vcore regulator on the motherboard, which provides the low voltage high current supply for the CPU core.

As ssteinberg says, look for leaking and/or domed top capacitors near the CPU. They tend to fail before the CPU.

A useful experiment is to remove the CPU and connect the 4 pin connector.  If it won't power up, you certainly have motherboard problems but it does not mean the CPU is OK.

Providing you have some skill with a soldering iron, the capacitors can be replaced but you must get good quality replacements and you must replace all the capacitors in the Vcore regulator as those that look good now will be stressed and will fail soon.

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## drwook

no obvious physical sign of bad caps...  otherwise I'd be more than happy to reach for the soldering iron.  I'll check the board without the CPU tomorrow - if it does fire up we're thinking it's definitely the CPU is gone, right?  But if the same happens, then it's either 'just' motherboard or both mobo and CPU?

I'm starting to think about grabbing a new AM2+ board, seeing if the CPU is shot, and if so grapping an x6 phenom....  am I missing out on much if I try that rather than going for a 'real' AM3 board do you think?  with xmas coming it's the wrong time to be dropping the best part of an unexpected £400 on cpu/mobo/ram....

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## Chiitoo

I have been playing around with AM2 and AM2+ boards too much, mostly the cheap/mid priced ones.

I would definitely suggest you go for a "real" AM3 board from the start as a lot of times, you might need at least a BIOS update to get support for the new CPU.

However, try to make sure the MOBO actually HAS that support already, because AM2 CPUs wont fit into AM3 socket, so you could end up like me, having AM2, AM2+, AM3 boards and CPUs, BUT your AM3 board needs a BIOS update to get support for the AM3 CPU.

This happened with a Gigabyte board, it was advertised as being ready for the 6x Phenom which it really was not...

It would crash a lot at boot time, but with some weird luck, I managed to get into the built-in FLASH utility and update the BIOS from a USB stick without any problems, lucky me.  Though, I had performance problems with WinXP, win7 would crash all over with bluescreens and not, Gentoo has crashed 2 times I think...  However, it might be a problem with the PSU too, I don't know...

You'll need new memory sticks for the AM3 board as well though, but I would recommend going for it, still.

You might or might not be able to tell any concrete differences but still.

Just my thoughts, anyways.  ^^

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## luscinius

If you get an AM3 mobo you will need to replace both RAM and CPU. Phenom II 920 and 940 were the first Phenom II models, and they were socket AM2+. The later AM3 models are backwards compatible, and those can go into an AM2+ mobo (probably with some BIOS update); but AFAIK, an AM2+ CPU won't go into an AM3 mobo. http://en.wikipedia.org/wiki/List_of_AMD_Phenom_microprocessors#Phenom_II_series I agree that most likely it is mobo that is dead, and I would also try replacing/fixing it first.

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