As previously discussed, we must run the memory at the same speed as the FSB on Athlon/Duron systems, so in this case memory overclocking and increasing the FSB should be thought of as one and same. You first determine the default frequency of your memory, 1MHz higher than that frequency is the point where overclocking begins. The memory's frequency depends upon the frequency of the FSB. Characteristics of that dependency are defined by memory ratios as explained before. Other aspects to memory overclocking are memory timings and of course the amount of voltage supplied.
The front side bus is what connects the processor to the rest of the system. To improve performance, you increase the frequency therefore shortening the time it takes to transfer data. Improving overall system performance is the process of removing bottlenecks and making paths that aren't already bottlenecked as fast as possible. Since FSB frequency and Memory frequency are most times made to be the same, this poses a problem - as overclockers look for the highest possible FSB while the memory may struggle behind at a slow speed. Many boards (usually older ones) will run the memory bus at the same speed as the FSB and there is no way of changing it. Most newer boards allow you to alter the speed of the memory bus in relation to the FSB.
There is really no point having a high FSB, if the memory can’t keep up. When the memory or any other component is holding back system performance, this is called a “bottleneck”. An example of a memory bottleneck would be if you were running your memory at DDR 333 MHz with a 400 MHz system bus. The memory would only be providing 2.7GB/s of bandwidth while the bus would be capable of transmitting 3.2GB/s of bandwidth. A situation like this would not help overall system performance.
Think of it like this; let's say you had a highway going straight into a mall, with an identical highway going straight out of the mall. Both highways have the same number of lanes and initially they have the same 45mph speed limit. Now let's say that there's a great deal of traffic flowing in and out of the mall and in order to get more people in and out of the mall quicker, the department of transportation agrees to increase the speed limit of the highway going into the mall from 45mph to 70mph; the speed limit of the highway leaving the mall is still stuck at 45mph. While more people will be able to reach the mall quicker, there will still be a bottleneck in the parking area leaving the mall - since the increased numbers of people that are able to get to the mall still have to leave at the same rate. This is equivalent to increasing the FSB frequency but leaving the memory frequency/bandwidth unchanged or set to a slower speed. You're speeding up one part of the equation while leaving the other part untouched.
Sometimes the fastest memory is not always afforded or available. In this case, more focus should be placed on balancing the FSB and memory bandwidth while still keeping latencies as low as possible AND while still maintaining CPU clock speed (GHz). The benefit of a faster FSB (and higher bandwidth) will only become more and clearer as clock speeds (GHz) increase; the faster the CPU gets, the more it will depend on getting more data quicker.
The memory timings can also play a role in how far the memory will go, in keeping with the FSB. Lower timings (numbers) will hinder how fast the memory can run, while higher timings allow for more memory speed.
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by Exit  edited by FastEddie
last modified: 2004-02-08 18:43:07 |
