upgraded cpu doesn't like 8 gigs of memory?!

[atomiser]

hi there,

i've just done a small upgrade from an e4500 to an e6550 to enable virtualisation support on my esxi box.

with the e4500 it would run with 8 gigs in all day long. now it's horribly unstable.

i've re-installed it from scratch, and also tried installing several versions of windows.

im here now on 7, with 4 gigs of ram and it's fine. as soon as i bump it back up to 8 it just hangs.

no bsods or anything like that, just becomes unresponsive. any ideas where to start troubleshooting?

thanks.

 

[atomiser]

the memory configuration is 4x 2gig sticks. its all ocuk value stuff, bought as 2x 4 gig kits. they were bought at different times, so each kit is from a different vendor. one pair is transcend and the other is ocz. i've tried each pair seperately and both behave the same - stable in their own right, unstable when both are used simultaneously.

this has *only* happened since i upgraded the cpu. the old cpu was an e4500, with an fsb of 800 matching the ram. the new cpu is an e6550, with an fsb of 1333. would this matter? i checked motherboard compatiblity (gigabyte g33m-ds2r) before i purchased the chip and it has been supported since bios f3. im on bios f7 at present. bios f8 and f9a are available.

i should also add that initially i thought it could have been temperature related, as i used the existing heatsink and fan, and i thought perhaps i didnt have a good seal since i didnt have any new thermal paste so had to use what was already on there.

i have, however, since cleaned the cpu up and used a brand new oem intel heatsink and fan (left over from the e4500, since i used an aftermarket cooler previously) and the problem is the same. checked in the bios and the chip isn't going above 40 degrees celsius.

 

[atomiser]

hi there,

thanks for everyones suggestions.

when i checked the bios it appeared the board was trying to actually run the memory underspec at 533mhz?! i manually changed it back up to 800mhz and it has been rock solid since!

cheers.