Overclocking Basics (Read before asking overclocking questions)

[mystifmagic]

Overclocking your AMD System

Overclocking your processor is broken down into two sections. Bumping up the multiplier, and raising the fsb. To begin, you must know that the processors speed is figured by the simple equation, fsb speed times the multiplier. Say your proc is at 166mhz fsb x 12(the multipler). This equals 2000mhz(2Ghz), the processor speed for this example. Now, how high you can overclock is never a guarantee and depends greatly on the quality of your parts.

You could easily raise the multiplier a notch at a time to raise the processor speed, if that's what you want to focus on. Every time you bump it up, run some games or stability testing programs(superpi, sandra, prime95, 3dmark or others). If it becomes unstable, you should raise the vcore. I wouldn't let your temps go above 55C(download mbm5(motherboard moniter 5) to check temps). Also, keep the vcore at 2.0v or under for now.

Now, raising the fsb helps improve the performance of your system as a whole by increasing data transfer rates of just about everything in your system. You can bump up the fsb by about 3-5mhz at a time, doing stability testing all along. If you want to work on this first(that's usually how most do it), it's advised to lower the multiplier some, to keep the cpu speeds at or below stock speeds at all times, to rule out to processor as what is holding your overclock back if you run into stability problems. If you do run into stability problems, raise the vdimm and/or vdd or raise the memory timings. Great memory timings are 2-2-2-5 while relaxed ones are 2.5-4-4-15(the last one doesn't matter once it's that high usually, also, it has been decided that setting it to 11 gives the best performance on nforce2 motherboards.)

If you don't know where to raise the voltages and do all of this, it is located in your bios. This is found when first booting the system and usually holding the Delete key.

DDR:

fsb/d1*d2*2= memory speed (aka DDR speed)

fsb stands for front side bus.
D1 stands for divider 1
D2 stands for divider 2
Dividers can and will be found in bios, likely within close promixity to your fsb itself. Dividers control whether your memory is in sync or in async with your front side bus. A 'sync' divider will always be 1:1, while an async memory divider will be anything other than it. Async dividers can offer either higher bandwidth or lower bandwidth than sync'd memory dividers.
2 is multiplied because it's DDR (Double Data Rate)
For Dual Channel systems: another 2 should be added like this:
fsb/d1*d2*2*2= memory speed.
Again, the reason another 2 is added is because it is Dual Channel, meaning that the theoretical bandwidth is multiplied by 2, effectively doubling the bandwidth.

Example:
My front side bus is 133, and my memory divider is 4:6, I'm running a single channel system so the algorithm to be used would be:

133/4*6*2=399 (aka DDR400)

To find out the theoretical bandwidth, a smiliar algorithm can be used, which is as follows:

fsb/d1*d2*bit= theoretical bandwidth

Note: Current DDR is 16 bit, so use 16 in place of 'bit' whenever finding things out, using this formula.

Example:
My front side bus is 133, and my memory divider is 4:6, I'm running a single channel system so the algorithm to be used would be:
133/4*6*16=3192 or pc3200 (as it is usually rounded by manufacturers)

This means that I'm getting theoretically 3.1mbps bandwidth.


Some helpful links:

Information/Temperature displays:
Motherboard Monitor
CPU-Z
WCPUID

Stability testing/benchmarking:
SiSoft Sandra
Prime95
SuperPi (direct download)
3dMark 2001SE, 3dMark 03, PCMark 04
Aquamark

Misc:
Clock-gen for Nforce 2
Voltage changing program for NF7 boards

Another full OC guide thanks to Ranger 2992

This guide was written by speedyaxon and added to by Candyman and CrawlingEye.

[mystifmagic]

Overclocking the A64


Overclocking an A64 is a balance between getting the maximum memory speed and maximum cpu speed at the same time by utilizing the vitually unlimited HTT bus. Dropping the LDT multiplier to a low number like 2x can allow one to clock generally over 300 and sometimes over 400mhz HTT on an nforce3 board. With this ability, you have to find the ideal HTT and cpu multiplier combination that maximized your cpu speed, while using the right divider on the RAM to get the best blend of memory timings and frequency. Maximizing memory speed can be tricky on the A64 because of the way the integrated memory controller determines the memory frequency:

Memory frequency is determined by both CPU multiplier and RAM divider, unlike any other system.

The Memory Frequency (f) = CPU Frequency (c) / [Multiplier (m) + Divider (d)]

f = c / (m + d)

where d is 0, 2, or 5 (1:1, 6:5, 3:2)
m is an integer, always rounded up (therefore .5 multi's will round up)

so if you run 2.2ghz 1:1 on a 10x multiplier your memory frequency is 220mhz

220 = 2200 / (10 + 0)

but if you run 2.4ghz on a 9x multiplier (267x9) 6:5 your memory frequency is NOT 222 (267 x .83), but rather 218.

218.18 = 2400 / (9 + 2)

EXCEPT in 1:1 with an integer multiplier, then it works like always:

memory frequency = bus speed.


The easiest solution when overclocking an Athlon 64 is simply to get RAM that is well paired with your processor so that you can simply run 1:1 while maximizing both. If you get a newcastle cpu, plan on speeds of 2.5-2.6ghz with conventional cooling and accordingly buy RAM that is capable of about 266mhz or thereabout with good timings. If you are buying a clawhammer, planning on speeds of 2.4-2.5ghz is more reasonable and therefore the memory you need would not have to go quite as fast to get the most out of the processor. With winchesters or higher speed clawhammers and newcastles, you may have to play the divider game or get some very good RAM.

Athlon 64 chips are also very sensitive to the ras:cas latency of the memory. while other timings are not as important as they are on other platforms, maintaining a low ras:cas value is crucial to getting maximum performance. Therefore, it may be neccessary to test your memory and system performance at various speeds with various ras:cas latencies to determine the best setting for you.

This guide was written by eshbach