memtest errors: always because of faulty RAM? or too high OC?

[IanM]

If memtest shows errors at high speeds around the maximum the RAM is rated for, but is fine at 'normal' speeds (1333-1600) does that suggest that the RAM is definitely faulty at its' rated speed? or does it suggest that the OC is too high for the CPU's memory controller?

How would you prove that the memory is faulty, rather than the CPU just isn't able to cope with the OC?

 

[drescherjm]

Could be either. Currently Intel CPUs specify support for DDR3 1333 maximum with DDR3 1600 support coming to lga2011. And I believe all current AM3 processors are still officially limited to DDR3 1333 with 1866 coming for BD.

Also if you are using more than 1 dimm per channel (4 slots filled on lga1155/1156 or AM3 or 6 slots filled on lga1366) overclocking the IMC may be more difficult.

 

[IanM]

My experience with this is pretty much what I expected, variation according to the individual CPU:

with 1st CPU:
1 DIMM per channel it's ok to max out the RAM speed no problem. 2 per channel requires reducing BCLK and limiting the RAM speed to below its' rated maximum.

with 2nd CPU:
1 DIMM per channel won't go as high as the first CPU (but still pretty high) and 2 DIMMs per channel requires limiting the speed further
​

I was just wondering what happens if you buy (or sell) some RAM and it doesn't work at the rated speed, but it's OK when used within Intel/AMD specs.