PDC22G9200ELK is a PC2-9200 2 GB memory kit from Patriot, meaning that it can be run up to 1,150 MHz maintaining its programmed timings (5-5-5-12), being targeted to serious overclockers. We reviewed this kit and we will see if this kit is really capable of running at 1,150 MHz and what are the advantages of using PC2-9200/DDR2-1150 memories over regular ones.

A lot of people think that the memory modules will always work at their labeled clock rate. This isn’t true. Who decides what speed your memories will run will be your motherboard (in the case of Intel processors) or your CPU (in the case of AMD processors). If you replace your DDR2-533 memories with DDR2-800 ones it is not guaranteed that your new memories will be running at 800 MHz. Sometimes, due to misconfiguration, they will still be running at 533 MHz (you need to enter the motherboard setup and set the new memory clock rate). In other cases, you may be using an old motherboard that only recognize up to DDR2-667 and your DDR2-800 memories will be running at 667 MHz, not 800 MHz. AMD processors use a funny clock division scheme where your memory may be running at a lower clock rate (for example, with Athlon 64 X2 5000+ DDR2-800 memories work at 742 MHz – click here for a detailed explanation on this issue).

A good way to check the real clock rate your memory modules are using is by running a program called CPU-Z, and clicking on the Memory tab.

So, why we are telling you all this? Because if you buy this memory module from Patriot thinking that it will automatically work at 1,150 MHz you are wrong. If you didn’t set any overclocking on your PC it will work at 800 MHz (or a little bit less, if you have an AMD processor) or at 1,066 MHz, if you have an Intel processor and your motherboard is capable of setting your DDR2 clock at 1,066 MHz (for example, on motherboards based on Intel P965 and nForce 680i chipsets). In this case you need to enter the motherboard setup and configure the memory at 1,066 MHz or it will work at 800 MHz.

Then what is the use of DDR2-1150 memory modules? Overclocking. If you are not into overclocking, this memory isn’t for you.

If you do overclock, then this memory module may be a terrific product for you to expand your computer’s overclocking capability.

Let us explain this further. On the majority of motherboards available on the market there is no separated clock generator for the memory modules, so the clock generator used by the CPU will be also used by the memory (one good exception are the motherboards based on nForce 680i chipset, where there is a separated clock generator for the memories).

Overclocking is done by increasing the CPU external clock rate and since the memory clock rate is tied to the CPU external clock, you will automatically overclock your memory as well when you overclock your processor.

Let’s give you a real example. Let’s say we have a Core 2 Duo CPU with an external clock rate of 1,066 MHz. The real external clock rate of this processor is of 266 MHz. As Intel CPUs transfer four data per clock cycle they are rated as having an external clock rate four times higher than the real clock rate that is being used. Let’s also say that we have two DDR2-800 memory modules running at 800 MHz. The real clock rate of these modules is of 400 MHz. Since DDR2 and DDR memories transfer two data per clock cycle, they are labeled as if their clock rates were two times higher than their real clock rate.

On a motherboard using a single clock generator (the majority of boards found on the market) the 400 MHz memory clock rate will be generated by multiplying the CPU external clock rate by 1,5 x (this is also referred as 3:2 ratio).

So what happens with your memory when you overclock your CPU external clock rate from 266 MHz to 290 MHz? They will be working at 435 MHz (870 MHz). So they will also be overclocked.

Let’s say that increasing your CPU external clock rate above 290 MHz your system was unstable, so you came to the conclusion that this is the maximum clock rate your computer can achieve.

However, one question is still on the air: what was limiting your system from going beyond 290 MHz? Was the CPU? Or was the memory?

By replacing your DDR2-800 memories with a higher-grade memory you will be able to check this out. For instance, if by installing DDR2-1066 memories – where the manufacturer guarantees that the memory can work up to 1,066 MHz – your system works fine when increasing your CPU external bus over 290 MHz, it means that your DDR2-800 memory was the limiting factor for achieving a higher overclocking. However, if you are not able to push the clock rate above 290 MHz this means that another component is limiting your overclocking (maybe the CPU itself).

These memory modules from Patriot are guaranteed to work at 1,150 MHz, so you may be able to achieve higher overclocking with your CPU in the cases where the memory is the limiting factor.

Of course when working at a higher clock rate the memory is capable of delivering a higher transfer rate, but the main goal of using these memories is allowing you to achieve a higher CPU overclocking – the extra memory performance will be a consequence.

Gabriel Torres is a Brazilian best-selling ICT expert, with 24 books published. He started his online career in 1996, when he launched Clube do Hardware, which is one of the oldest and largest websites about technology in Brazil. He created Hardware Secrets in 1999 to expand his knowledge outside his home country.