async?

[flboad]

I've read all the guides for overclocking and ram stuff and i've read it a couple times. But i still have a little haze when it comes to a couple things. First the async mode.

i used WCPUID. and got the following.

Internal Clock 1533.38 mhz
system clock 133.34 mhz
system bus 266.67 mhz ddr
multiplier 11.5

My system specs are AMD athlon xp 2600+
1 gig Ultra ram

Now my question is, should i make the system clock higher to the bus speed or should i make the bus speed lower to the clock? Because async is bad for amd.

 

[Monkey34]

What kind of memory are you running? ddr2100,3200,etc.
TAKEN FROM MEMORY FAQ STICKY(good to read)
Actual clock speed(fsb)/effective transfer rate(memory):
100/200 MHz => DDR200 or PC1600
133/266 MHz => DDR266 or PC2100
166/333 MHz => DDR333 or PC2700
185/370 MHz => DDR370 or PC3000
200/400 MHz => DDR400 or PC3200
217/433 MHz => DDR433 or PC3500
233/466 MHz => DDR466 or PC3700
250/500 MHz => DDR500 or PC4000
267/533 MHz => DDR533 or PC4200
When the memory frequency runs at the same speed as the FSB, it is said to be running in synchronous operation. When memory and FSB are clocked differently (lower or higher than), it is known to be in asynchronous mode.
When looking at the AMD-supporting chipsets async modes are to be avoided like a plague. AMD-supporting chipsets offer less flexibility in this regard due to poorly implemented async modes. Even if it means running our memory clock speed well below the maximum feasible for a given memory, an Athlon XP system will ALWAYS exhibit best performance running the memory in sync with the FSB. Therefore, a 166FSB Athlon XP would run synchronously with DDR333/PC2700 (2*166) and give better performance than running with DDR400/PC3200, despite its numbers being bigger. To achieve synchronous operation, there is usually a Memory Frequency or DRAM ratio setting in the bios of your system that will allow you to manipulate the memory speed to a either a percentage of the FSB (i.e. 100%) or a fraction (or ratio) i.e. N/N where N is any integer available to you. If you want to run memory at non 1:1 ratio speeds, motherboards use dividers that create a ratio of CPU FSB: memory frequency. However, intrinsically, it is possible to see the problem with this and why synchronous operation is preferable on all PC platforms. If there is divider, then there is going to be a gap between the time that data is available for the memory, and when the memory is available to accept the data (or vica versa). There will also be a mismatch between the amount of data the CPU can send to the memory and how much the memory can accept from the CPU. This will cause slowdowns as you will be limited by the slowest component.
Here are three examples illustrating the three possible states of memory operation:
200MHz FSB speed with 100% or 1:1 (FSB:Memory ratio) results in 200MHz memory speed (DDR400)
Such a configuration is wholly acceptable for any AMD system, memory should be set this way at all times for best performance. Asynchronous FSB/Memory Speeds are horridly inefficient on AMD systems, but may well be the optimal configuration for P4 systems.
200MHz FSB speed with 120% or 5:6 (FSB:Memory ratio) results in 240MHz memory speed (DDR480)
This example shows running the memory at higher asynchronous speeds. Assume we have a Barton 2500+ which by default is running at a FSB of 333 MHz (166 MHz X 2) and we also have PC3200 memory which by default is running at 400 MHz. This is a typical scenario because many people think that faster memory running at 400 MHz, will speed up their system. Or they fail to disable the SPD or Auto setting in their bios. There is NO benefit at all derived from running your memory at a higher frequency (MHz) than your FSB on Athlon XP/Duron sytems. In actuality, doing so has a negative effect.
Why does this happen? It happens because the memory and FSB can't "talk" at the same speeds, even though the memory is running at higher speeds than the FSB. The memory would have to "wait for the FSB to catch up", because higher async speeds forces de-synchronization of the memory and FSB frequencies and therefore increases the initial access latency on the memory path -- causing as much as a 5% degradation in performance.

 

[flboad]

166/333 MHz => DDR333 or PC2700