I can't get the mobo to see all 6GB of the Mushkin RAM. However, I can get all 6GB of "Patriot" RAM 3x2GB DDR3 PC3-10600 (1333MHz) to be recognized.
Obviously the Mushkin RAM worked fine for the System Builder Marathon. Does the fact that the Mushkin RAM only show 4GB's whereas the Patriot RAM shows 6GB, possibly mean I have a bent pin on my CPU?
Now 9 out of 10 times the mobo boots correctly seeing all 6GB's, the other 1/10th of a time the mobo reports 4GB at POST, and right after "Verifying DMI pool...", POST reports DRAM size mismatch and reboots immediately. This behavior occurs constantly with the Mushkin RAM, and apparently the only way around it is to enter BIOS and quit without saving, then at least the box boots with 4GB detected.
BTW, once booted the system runs well, either with all 6GBs detected or 4GB.
Win7 always sees 6.00GB installed(4.00 GB usable) with Mushkin.