According to AMD, the A4-5300 only supports up to DDR3-1600 memory. The default bus speed is 100 MHz, so a 24:3 DRAM:FSB ratio runs the memory at 1600. However, I can get the bus speed up to 137+ MHz, which gets the memory running stably at close to 2200. But when I bump the ratio up to 28:3 or 32:3 and set the bus speed back to 100 MHz (i.e. running the memory at 1866 or 2133), the system fails to post and I have to clear the CMOS. That's running the XMP profile.
So is it that the CPU supports speeds above 1600 but not ratios above 24:3? Or is this a motherboard thing?