AMD FX-8120: can't use 6/8 cores

XP64 supports 2 cpu's with as many cores as each chip has, we use it at work with i7's. Any option in bios to disable core / hyperthreading.

install xp service pack 3, see if that changes anything

I know it supports; it was working well before.  
I couldn't find anything related to hyperthreading in BIOS. Do you have any idea how else it can be named?


There's no SP3 for XP64 afaik (only for 32bit XP which should be equivalent to SP2 for XP64). Downloading SP2 now and will try it!

win pro sp2 supports 8 cores ,

Why did you reinstall Windows?

Did it work fine before you reinstalled it?

If it ever worked with all 8 cores, how long did it work for?

When you did reinstall Windows, how did you go about doing that?

1. use single one 80gb SSD) and had to resolve it asap to continue work because of deadline. So it was much quicker to reinstall whole system and set up a new temporary database than trying to fix the problem and fail to do that eventually. I simply couldn't risk I waste 2 hours and still would have to reinstall it after all...

2. It was all OK, except there're some whole system lags in last hour or so which I believed where related to database problem (they were for sure, at least partially).

3. Yes it did for about 2 months since I built it.

4. Not sure what you mean

SP2 installed, problem solved (it shows weird CPU temperatures, but I can live with that^^)...

Asking in the forums was a great idea: I tried a lot of things but the one of the simplest solutions didn't come to my mind.

Thank you all for the help!

Based on your answers, the most likely problem was a corrupt Windows install.

I don't know if you did a repair, a restore, a reinstall over the top, or what the case is, but it sounds like Windows needs to be blown away completely and reinstalled.

What I would suggest is that you put in the Windows CD, make sure to delete all the partitions, and then install again fresh with no pre-existing files remaining.

Even if that sounds like what you did already, I would do it again.

I still don't understand what the original problem was, but you might additionally want to run some hardware tests when you get some free time. MemTest86+ can help with RAM, AIDA64 or Merseinne Prime can help with the CPU, and Windows itself should be able to check for hard drive errors.

- Edit - It did turn out to be a Windows install problem it seems. Glad it is sorted out, at least.