DDR2 Memory Timings

Am having trouble getting ram to work on my new asus p5rd2-vm motherboard.
Am on my 3rd lot now and still getting heaps of memory related errors.

Got 2 x 512mb crucial ballistix ddr2 5300 667mhz ram in post this morning
and am getting exactly the same settings.

anyway im about to power it back on and try putting the timing settings in
manually which i have as 3-3-3-12

The thing is i cant seem to find out what value i should put for 'refresh
rate select'? the input range is between 15.625us and 125us

Thanks


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