i5 2310 not working with 2 or all cores

Can anyone give advice as to the faulty component Board or chip?

Have a new bare bones system im building for a client but the PC will only run on 1 core or 3 cores?

anything else and the system freezes in BIOS, and if it gets past BIOS will restart system after getting to the point where windows starts animation at start up.

Im not sure what the is the faulty component

The system was fine at first as I was in OOBE adding oem info and latest windows updates then the system just restarted and problems since then. Its the first time i have seen this fault specificly with cores.

memtest shows memory is fine
latest bios updates applied to board
i5 processor reseated and all cables are fine
changed memory config on board to every combination thinkable single sticks and both sticks.
Also tried swapping PSU same results

its a puzzle to me and would like to know if anyone else has had the problem and resolved it.

specs

i5 2310 (BX80623i52310)
2 x 4Gb (KVR1333D3N9/4G)
System Asus 1155 Vintage8-P8H67E DDR3 / GB lan / HDMI / zwart (Barebone)

All parts are on QVL

http://www.asus.com/Barebone_PC/V_Se...H67E/#overview

totally lost as never seen this fault before.

Dave

Amendment *Memtest crashes shortly after starting test*

You have a hardware issue. I would suspect board first, but could be the actual CPU.

thanks Nat, will order both today and update this post when i find out the faulty component.

Turned out to be CPU

I would have guessed MB! Which is why i don't like to guess.

ha