Overclocking the modules
There are a number of different ways we could have chosen to overclock the DDR-2 memory modules in this article. We choose to go with the highest possible clock speed at loose (slower) timings. We choose this option since the memory timings of DDR-2 at the moment is sill slow compared to low latency (2-2-2-5) DDR memory and until memory timings of DDR-2 tightens up to levels of DDR technology, higher clock speed will remain more important.
Editor Note: In fact, soon we will publish an article which looks at a range of different memory and CPU settings to help determine which combination is your best choice for DDR-2 memory.
Using the classy ASUS P5AD2-E motherboard based on Intel's 925XE chipset and Intel Pentium Extreme Edition processor clocked at 3.46GHz, we had a perfect platform in place for our DDR-2 overclocking. The motherboard allows for VDIMM (memory voltage) selection from 1.7V up to 2.2V which is plenty for DDR-2 and as well as this the board is generally known as a good overclocker.
To even things out a little, we made the timings for each overclocked module 5-5-5-8.
- OCZ DDR-2 Overclocking
We'll start with the OCZ PC-5400 Performance Series DDR-2. First of all we raised the VDIMM to 2.2V and set the memory divider to 3:4. We were able to set the CPU FSB to 315 x 12 (3.78GHz) which resulted in the memory running at 420MHz (DDR-840) or a little over PC-6700. This results in the memory running 154MHz over default and we also receive a good little CPU overclock of 322MHz.
For air cooling and considering we are in our Australian summer at the moment, we were very pleased with the results of the OCZ memory and we reckon the other modules will have a tough time keeping up especially since the OCZ memory is tested at their factory to work well at 2.2V which we consider a huge advantage.
- Corsair DDR-2 Overclocking
Next up is Corsair and at the start of testing we thought OCZ might have something to worry about since the Corsair was able to post at about 427MHz at 2.2V but the system locked up before it had a chance to get into Windows.
The Corsair memory has a voltage rating of 1.9V but it seems to us that while it will happily do 2.2V at some speeds, it struggles to handle 2.2V when the memory is pushed. The memory was able to pass some tests higher than our maximum stated clock speed but it would crash in other tests or just lock up randomly.
Using a VDIMM of 2.2V we were able to get a maximum of 413MHz (DDR-826) or a little over PC-6600 with the CPU FSB set to 305 x 12 (3.66GHz). While there is only a little difference in clock speeds between Corsair and OCZ, due to the way the BIOS is setup the OCZ memory provides a 120MHz clock speed increase on the CPU which will assist in making a difference when it comes to looking at our overclocked benchmark results.
- Kingston DDR-2 Overclocking
The last on the list is Kingston and unfortunately with the HyperX memory they sent us the maximum stable voltage we could achieve was 1.9V. We could get into Windows at 1.95V but would crash and lock up soon after.
So at a VDIMM of 1.9V the HyperX memory is handicapped from the beginning but we were still able to push the memory to 400MHz (DDR-800) or a little over PC-6400 with the CPU FSB set to 300 x 12 (3.60GHz) which is a big overclock over its default speeds but just not as impressive as what the OCZ and Corsair modules could achieve.
While there is only 27MHz different in memory clock speeds between OCZ and Kingston, the OCZ test system has a big advantage since the FSB is set 15MHz more which results in a CPU clock speed increase of 180MHz which will help make a difference when it comes to gaming performance and so on.
Burning in Memory
I wanted to address burning in of memory before we move onto the benchmarks since it is talked about a lot in our forums and in person with other people we talk with. In the past we have seen DDR memory provide good initial overclocks and then move on to impressive overclocks. We didn't change anything in the system nor did we improve cooling...some modules seemingly magically improve.
Of course though there is nothing magic about it but we have no science either to back it up - just like a new car, after it has had a chance to run in (or burn-in, in this case) some modules are able to overclock further. There is a good chance, especially with the Kingston memory, that if we were to run in the memory for a couple months it would be able to ramp up more and maybe run at a higher VDIMM but of course this is the case for the OCZ and Corsair memory modules as well.
Having said all this you shouldn't buy any of these modules expecting them to perform any better after a couple months of use - you might get lucky or you might not. It's just something to keep in mind.
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