Some guy at XS had a thread on timing configurations at DDR2 800 and from what I can remember, the CAS 3 gave the lowest scores, and by lowest I don't mean......dog slow but!, then move to CAS 4 and finally CAS 5.
Out of all configurations, he found that CAS 4-4-4 was the best way to run the timings at and CAS 5-5-5 came in 2nd and CAS 3-3-3 was, well, 3rd.
Basically the differences were very minimal and nothing to be alarmed but since that everyone is always in "the pursuit of performance"
, I've always recommend and use 4-4-4- regardless of what speed and ratio I use.
So 4-4-4-8 for DDR2 1000: http://valid.x86-secret.com/show_oc?id=128537
BTW, I wish I could remember which thread and which side of the forum that was.