I. AMD Athlon™ X2 Dual Core Processor BE-2XXX.
II. AMD Sempron™ Processor LE-1XXX.
Those are the last two cpus that received support. The newer bios versions (2.6) only affected a specific sound car and the usb code. You can try other cpus that fit the socket and they might work, but these are the last two that are guaranteed to work by ASRock.