Try Dram ref voltage for both channel A & B +12,5mV.

I got the board screaming now at 600FSB with 5:8 divider (DDR1920) 7-6-5-18 Tref 48 timings 32M stable!

I tried to stabilize these settings and couldn't get memtest86 test 5 without errors, not even with 2.21V.

Then i tried 2.17V and Dram ref volts +12,5mV on both channels and voila, stable as a rock!