Overclocking An A64 is like calculus, everytime you change 1 variable everything else will change
generaly i follow these rules when pushing an A64 cpu
Start with stock voltages, if you want to make some shortcuts it usualy a safe bet that 10% increase in stock voltages is okay for OC, Unless you have good water or cryo NEVER go above +15% Voltage, especialy with X2's and other 90 nano chips, Electromigration is a serious risk on this grade of sillicon.
drop your memory multiplier down so that it is NOT going to be an issue, you will need to watch this later on with higher FSB's, also drop the HT multi from 5 to 4 to prevent the HT from becoming a loose end in your early stage clocking, you WILL probably need to drop BOTH of these multipliers again once you hit a 250 FSB, IF you get that far.
Start with an instant 20Mhz bump on your FSB, this will most likely work without issue,
Proceed to bump the FSB up by 5mhz jumps untill you find you are not posting properly, if youre lucky you should be able to make it to BIOS to bring the FSB down by 10Mhz, this SHOULD make your core stable again, If necessary reset your cmos and go back up to 10mhz below your last FSB attempt.
once you hit this ceiling, you can go for your first burn test, i suggest just a quick hit of Pi to make sure the thing is running ok in the OS
After your Pi is running to satisfaction with no errors, you can begin your loving with the HT and ram
For starters, bring your HT so that your HTxFSB is as close to 1000 as posible you may have to bite the bullet at this stage and take the lower of the 2 multiples if youre between multipliers, dont worry about it too much just yet if youre comming in under 1000mhz with your closest multiple
now is the hard bit, your ram. Ram clocking is a bit of artistry in an overclocked AMD system, and many different BIOS's will have different ways of dealing with it, the most common one is called "post lock multiplier" which uses a sub multiple of the FSB to generate ramspeed
you are most likely running DDR 400 in your board, if this is the case, when your ram is set to 400mhz in the bios, it will actualy BE 2 times your FSB frequency :| so that if you are actualy running 250 Mhz FSB you are overclocking your ram to a Whopping 500Mhz, Probably too much for most ram moduals to handle
the easiest way to work your ram out is to divide the ramspeed you set in the bios by 200 and multiply it by your current FSB, this will generate your REAL ramspeed
say i have my DT-D43 ram set to 333Mhz in the bios, this is of course UNDER the rated speed for DT-D43, BUT with an FSB of 250 my ram will run at ratio 333(166Rclk/400(200Rclk) or approximately 0.83x250 which is infact a nice healthy 416mhz (208Rclk), which the ram should be quite happy at
Dont be afraid to increase a few timings on your ram for the sake of bringing it's Rclk as close to the FSB as possible, Amd64's LOVE Bandwidth and will suck it up in spades, latency on AMD is nowhere near as important as it used to be thanks to AMD's lovely internal memory controler.
Oh one more thing, If youre game, you can attempt to bring your ram gradualy higher using the ram multipler, just keep in mind that the speed you see in the BIOS is not the real speed of your ram
and be sure to do a good prime after every big jump in your memory speeds
Last but not least.
IF by some chance you finaly make it all the way to the end and wish to try the devil's fortune you can attempt to overclock your HT, THIS is the most unstable part of the entire system and can cause serious issues with things like sata hdd's and sound cards, it MAY be in your best interests to actualy drop your fsb a little to help bring the HT up to par with the 1000Mhz benchmark,
personaly i run a 4400+X2 on a DFI NF4 SLI-DR with ram running 510 @2.5,3,3,5 core running at a delicious 2.86Ghz prime stable,
good luck to you all
Mhz are a drug
Get high or die