I spent a LOT of time OC'ing my a8n-sli deluxe and the terminology on that BIOS threw me off for a good while.
Set HTT Multiplier to 3x
Set DDR to 333 (that's your mem divider - running ddr400 at ddr333 lowers bandwidth but allows for higher CPU-->RAM speed (HTT mhz)
Verify memory timings at 3-4-4-8 1T (you may get more OC by loosening these timings even more, but keep the 1T cmd rate)
Set CPU multiplier to 7x
Start raising memory speed (forgot the exact term in this BIOS) from 200mhz, starting at like 300mhz (300mhz = 250mhz with memory divider) and going up by 5mhz until you fail to load windows or boot. Then drop back down and start stress testing with prime95 until you achieve several hours of stability.
Once you've found your max memory speed (HTT = FSB = external clock) you start raising your CPU multiplier by 1x at a time. If you fail to boot at 9x then start lowering your memory speed until you get stable. You're looking for the sweet spot of CPU multiplier vs. memory mhz. And testing with prime95 at every step along the way (even for just ten minutes) will allow you to find that sweet spot.
Memory divider: 333/400 = .8325, also known as 5:4 as 4/5 = .8. So you take .8325 and multiply that by your HTT and you have your "actual" memory mhz, which will always be close to 250mhz on your OCZ ddr500. That's why I suggest starting at 300mhz, as 300 x .8325 = 250mhz. You might be able to get higher than 300mhz, maybe even substantially. A lot of people haven't had luck OC'ing any higher than 250mhz on ddr500 (it's what it's rated at after all).
So anyhow, if you get 300HTT x 9 CPU multiplier then you have yourself 2.7ghz at DDR333. Which is an excellent OC.
Make sure to read zebo's overclocking guide here on anand.
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