Overclocking guide for newbies here...

Originally posted by DanF
Just going to add some tips for A64 clocking at the bottom here:

If your wanting to try and find out how high your system will go then it's usually easiest to break down the process into 3 sections which will usually get you to within about 5% of your max speeds fairly quickly.

The 3 steps are:
Find your rams max settings
2nd find your cpu's max settings
3rd combine them together

(To really get the most you also need to take into account max HTT speeds for benchmarking results in 3DMark2001se)

1) mem speeds
First go in to the bios and set the HTT multi down to 3 and also set the cpu multi down to say 7 and leave the memory set to either 200 or 1:1 setting with std timings (probably around 1T - cas 2.5 - 3 - 8 - 3). You then need to get hold of the latest version of a utility called memtester86 and make it into a bootable floppy. You also need to lock your AGP / PCI slots, with the MSI K8n Neo2 you need to set the AGP clock to 67mhz to achieve a lock, other boards vary. Without the lock you’ll struggle to get a high FSB. Other Neo2 board tip is use memory slots 1 & 2, also only use the two sata headers that are closest to the cpu.

Then you need to start raising the CPU FSB in steps of 5 and then run a complete cycle of memtester and keep on going until you get errors. Then you can either try and raise the memory voltage and see if the errors go or you can just use the last stable setting (trying to get the last 1-2 fsb is not really nessacery here). The last thing to do is to try and lower your memory’s timings one at a time and run memtester. This will give you a good fsb speed versus timings setup.

Do's:
Always keep either CPC on or the 1T timing on. It's vital for a fast A64 setup (with it off you'll probably need an extra 40+fsb mhz to be equal).
Don’ts:
Don't lower your timings over the std 2.5-3-10-3 unless it allows you to get much higher speeds as the A64 likes tight timings.
A system with mem at 1T-2.5-3-8-3 and only 200mhz will most likely be faster than one at 1T-3-4-10-4 at anything up to 240mhz, maybe faster.

2) cpu speeds
Then it's on to the cpu, make sure your case is fairly cool after an hour of prime95 or gaming, whip off the cover and stick you hand in, it should be only a few c over your room’s temps. If you have the std HSF then it's best to stay under 1.6v, a good HSF 1.65v, good water ~1.7v for your CPU voltage. The easiest way to have a cool CPU is to have a cool case (HSF can only dissipate heat at a certain rate + the temp of your case to begin with). Also there are reports of A64 mobo's having temp reading of over 10c out. You've been warned.

Now go in to the bios and change the settings to the highest CPU multi (say 9 for 3000, 10 for 3200, 11 for 3500). Keep the HTT multi at 3x. Go into the memory and set it to either 133 or 2/3 option.

Start to raise the FSB by 5mhz again and now use the latest version of Prim95 for 30-40minutes each time to test for cpu stability. You'll find points at each voltage level of maximum speed; write them down for future reference. As you find a max setting or induce errors then raise the cpu voltage one step and carry on going. Don't go over the above voltage limits.

Now you'll either find your ruff max OC and a high voltage or chicken out (probably the sensible thing to do) when you get to a certain point (2500 mhz and 1.68v for me on water cooling). Note that this is only your ruff max setting as you now need to move on to step 3 which puts more pressure on your CPU.

Now you should have your wanted settings for memory and cpu speed. It's now a question of working out the best combination of multipliers, dividers and CPU FSB. Each time you do this you really need to test for stability for 3hrs+ in your favourite stress test. Your final setting should survive 12+hrs continues testing. Any bsod's etc will indicate system instability and you'll need to play with voltages or settings.

Tips are:
1) To start with, stick the HTT multi times CPU FSB to always give you less than or equal to 1000mhz (ie HTTx4 times CPU FSB at 245 = 980mhz) This setting doesn’t really give to much real world performance gains so just use 3 or 4.
2) Killer systems need high mem FSB with tight timings and high CPU speed. A fast system only needs a moderate cpu speed with tight memory timings (loosen the timings and you will need more mhz to compensate, you can easily get into a spiral pattern for very little real world gains).
3) Try and keep the CPU FSB under 300, there is always a combination that you can use to get a good result with a lower CPU FSB.
4) The A64 platform has the memory controller on the CPU, this means that you are always running a divider to the memory so the magical 1:1 ratio means very little. Using other dividers for the memory will give pretty much no performance hit
5) You want a power supply with a good 12v ampage line like 18a+ at least.
6) The A64 loves samsung TCCD chip memory modules check a list out HERE
7) The A64 has issues with older versions of Prim95 and Memtester86
8) Latest Prime95 still has issues when using Cool n' quite On setting.
9) Cool and Quite is dangerous if you have changed the CPU multi from default. When it switches back from the lower speed it will reset your CPU multi (example is system at 278mhz and 8x multi = 2502mhz, reverts to 2780mhz and will crash)
10) don't use the auto performance setting in the bios or the nvidia / ati booster setting, you'll get better results with your own fixed overclocking settings. Also the nvidia / ati setting increases you GPU clocks so if they are already near there limit, this can push the GPU over the edge.

So a couple of examples from my system.
max memory speed at 1T-2.5-3-8-2 mem timings is around 230
at 1T-2.5-3-10-3 it can do 240mhz.
CPU maxes out around 2500mhz @ ~1.68v

So following combination give me almost identical results with 2 being just less than 1% faster than 1 in real games:
1) CPU FSB 250, CPU multi x10 = 2500mhz, memory at 166 divider and 1T-2-3-8-2 = 208Mhz.
2) CPU FSB 278, CPU multi x9 = 2502mhz, memory at 166 divider and 1T-2.5-3-8-2 = ~230Mhz.

The following are about 4-5% behind the above two and again almost identical to each other:
3) CPU FSB 300, CPU multi x8 = 2400mhz, memory at 133 divider and 1T-2-3-8-2 = 200Mhz.
4) CPU FSB 300, CPU multi x8 = 2400mhz, memory at 166 divider and 1T-2.5-3-10-3 = 240Mhz.

So results 3 and 4 are a very interesting comparison of faster mem mhz vs tight timings, three of the timings are worse with a 40mhz extra clock and they score almost identical to each other.

Tests where done using SuperPi 1M, Prim95 benchmark, Quake 3, Doom 3 & CS:S tests. Note that 3DMark2001SE isn't very good at gauging system speed on the A64 platform, changing the HTT multi down one or two steps can loose you several thousand points however in the above games there is less than 1% change. If you get better clocks with HTT at 3x instead of 4x with a CPU FSB of less than 250 then that's fine and dandy.

A tip for Prime95 is to go into the Advanced / Priority setting and put it to 10. This will really work your pc out, and probably make it almost unusable while it's running. You might need a little password though that I’ve forgotten. Also it's been mentioned that Prim95v233 and Prime95v238 has some issues with A64's so try the Prim95v22 versions.

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smids said:

Smids' 'n00b Crash Course in Overclocking' Guide

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