What is a memory rating and why do they exist
A memory rating is an identifying label that is assigned to a type of memory module by the manufacturer. This label is usually constructed by looking at the timing characteristics of the module such as it’s CAS latency and its frequency. Memory ratings are assigned to a type of memory module in order to identify it based on its attributes. There are three ratings that you will be able to find; they are unknown, OEM and retail. Unknown is a rating which identifies that the memory has not had any official testing done on it and may or may not have any issues with it. OEM is a rating which identifies that the module has been tested and verified as a specific type of memory. Retail is a rating which identifies that the memory has been tested in a retail promotion environment by a third party.
Finally, from the name, you can tell that there are different types of memory ratings:
SDR – Accelerated SDR is manufactured for overclocking on high performance computers with intensive use. These modules are used in systems that are designed for overclocking. This type of module should not be used in standard systems with standard components.
ODD – Optimized Dynamic has better performance and timing characteristics than SDR. These modules are used in systems that are designed for optimal gaming performance. This type of module should not be used in standard systems with standard components.
SD – Standard Dynamic is manufactured for standard desktop and office systems that do not require intensive use from the system. These modules are used in systems that are designed for typical usage from the system, such as office work or web surfing. This type of module should not be used for any type of overclocking due to timing limitations.
How to identify the fastest memory
You can identify the fastest memory by looking at the memory rating on the module. Retail rated memory will be faster than OEM rated memory because retail is more widely tested. The unknown rating is not as good of a quality and most likely will not work as well as retail or OEM rated memory. Unknown rated modules might not boot your computer at all or might boot your computer but you might be missing some functionality because of the modules. Retail rated memory is usually always better than OEM rated memory.
You can also identify the fastest memory by the speed that they operate. There are many different types of DDR such as DDR1, DDR2, and DDR3. The speed is normally written on the module itself or in the user manual for easier identification. The faster it operates, the better value you will be getting because it will be faster than slower rated modules in some cases.
What factors influence the speed of a memory module
CAS Latency, or CL, is a very important factor in determining the speed of a memory module. A higher CL will result in increased performance. However, a lower CL might be better if you are trying to run your memory on a lower frequency. For example if you had an 800MHz CPU and were trying to get the most out of your memory by running it at DDR400, a higher CAS latency memory module would be better then a lower CAS latency module. Since the lower frequency memory will operate at a slower data rate, the shorter CAS latency will result in improved performance.
The key is to understand how it all works together.
In addition to CL (CAS Latency), there are several other factors that influence the performance of a memory module. The most important of which is its speed rated, or labeled as PC3200, DDR400, etc..
The benefits of using a fast memory module
There are a few benefits to using a fast memory module. A faster memory module will be able to transfer information between the CPU and memory modules faster. However, it is important to note that there is a limit on how fast the CPU can talk to the memory modules. This limit is set by the front side bus and is around 66Mhz currently. To get around this, you can use a dual channel configuration which will allow you to have two memory modules working together in parallel to the CPU. This effectively doubles the bandwidth of your system, meaning that you will be able to transfer twice as much information between the CPU and memory modules at once. However, there is a limit on how fast a single memory module can run, and this is currently just under 200Mhz. There are several other reasons for wanting to use a fast memory modules, such as:-
* Increased bandwidth – If you are running a dual channel system and will be accessing information in both channels at the same time (such as when playing a game) then it may be worth your while to use the fastest memory module possible. This will allow you to transfer the most information between the CPU and memory modules at once.