Asus P5E3 Pro memtest speeds 4GB / 8GB

[tgourley01]

I have a Asus P5E3 Pro and a set of 2x2GB F3-12800CL9D-4GBNQ w/Q9400.
(9-9-9-24) (that board has the X48 NB)

I overclocked the (base) FSB to 400 (as listed in the BIOS) and this took the CPU to 3.2Ghz and the memory rate up to DDR3-1600. Memtest reported this as a little more than 6GB/s throughput.

I have been running this configuration rock solid stable for 2 years solid. (Windows 7 64bit)

I purchased another set of 2x2GB F3-12800CL9D-4GBNQ to max out this board. (same model and speeds, 9-9-9-24)
The new set (installed in isolation) memtest reports the throughput is 5.4GB/s for the same 800Mhz memory clock. I have tried tweaking just about every other value and nothing increases this value. (including NB dividers etc.)

If I install all 8 GB (4x2GB) (2x old, 2x new) memtest reports the rate is 4.8 GB/s.
Tweaking like crazy never yields any improvement on this.
(running all 8 was trickier, I did have to push up some of the voltages and force some of the memory timings to be stable, but nothing drastic)
(CPUz reported different SPD vals and I tried those as well)

My questions are:
1 - Can I trust the throughput reported by memtest? (it is reporting the memory clock and timings accurate...)
2 - Why can't I get the new 2x2GB set to run as fast as my old set? (6.0 GB/s)
3 - Is it expected that using 2 sets be even slower than the slowest set? (4.8 vs 5.4 GB/s)

Thanks!
Tim

[Tradesman]

1. Within reason, as with all testing software it may not be fully accurate

2. May be in part the newer programming in the SPD that is meant to improve performance in newer mobos

3. The 4 sticks vs 2 puts additional stress on the MC, mobo, and even CPU....could try increasing DRAM, NB and even vCore to increase performance of the sticks (in small amounts and prob want to benchmark as you go to see increases and what best provides them