[GIGABYTE GA-X58-UD3R] Memory drops from 6gb to 4gb at any speed above 1333mhz

Hi all,

I have GIGABYTE GA-X58A-UD3R mobo with CORSAIR XMS3 6GB (3x2gb) and i7-930. Latest BIOS version (F5).

IOH voltage at 1.3v
VTT voltage at 1.5v
Memory voltage at 1.64v (1.65 is memory max, but bios only allows .02 jumps)
CPU voltage at 1.1v (tried at 1.3v as well)
Memory tests (memtest86) are running without errors on all attempts listed below

The memory should be able to run at 1600mhz. Default settings keep the memory at 1066 so I enabled XMP and rebooted. Speed jumped to 1600, but now I only have 4GB visible at the post.

At this point, I went back to XMP and changed SPID from AUTO to 10, which combined with my base clock (bclk) of 133 brought my memory to 1333 and now all 6gb are visible.

I went back, dropped the CPU multiplier to 12, raised bclk to 200 and dropped memory SPID to 6 - 6gb visible at 1200mhz. Up the SPID to 8 - 4gb visible at 1600mhz.

Down bclk to 166, memory SPID to 8 - 6gb visible at 1328mhz

Up bclk to 170, memory SPID to 8 - 4gb visible at 1360.

Questions:
1. Is it true that when memory is running at 1600, only 4gb can be used?
2. If that's not true... what am I doing wrong?

Thanks in advance
X

Did you try a Bios upgrade.

Yeah. at F5 (latest available)...

I just came a cross Asuse X58 board doing the same thing as yours, I cant remember were the post was at.