This is most probably your problem!
The bus runs too slow when you populate all four slots.
The specs for the RAMS states 200 MHz and is only certified for that
speed. Trying to run them at anything less most yields possible timeout
problems.
I don't think so, Per. The modules are passive so they operate at whatever
speed is set by the controller.
They have to step the clock rate down because they're doubling the
bandwidth.
Another possibility could be that the matched sets are meant to be
installed one in bank 0 and the other in bank 1 for proper DDR operation.
I have not tried this, but I am game, especially since a close reading of the
manual yields an apparent contradiction. The manual states "The four DIMM
sockets are divided into two colors to help you identify the channel pairs