The A64 memory controller is more intelligent than all of us - it will look at the capability of your actual memory and decide a suitable overall clock speed to memory divider whether it be /11 or 12 or whatever - the HTT and max memory clocks are only a reference for the decision made at POST by the A64 itself. You make your BIOS decision and live with the A64 decision itself. Remarkable to say the least.
To Candymancan - yes voltage will increase along side temps at 1.7 and thus 1.8 under load - that's the spec not the board - for more RPM from cooler suggest upgrading the cooler itself as the board will only ever supply c. .38A of current along 12V all day long as called for my the
ATX spec for Fan headers.