Memory Speeds Tested
Crucial Ballistix Tracer Red 4GB PC-6400
- PC2-6400, 800MHz, 4-4-4-12 (EPP Enabled)
- PC2-9136, 1,142MHz, 5-5-5-15 (Max Overclock - 2.1V)
Corsair TwinX4096-6400C5DHX G
- PC2-6400, 800MHz, 5-5-5-18 (SPD Settings)
- PC2-8664, 1,083MHz, 5-5-5-15 (Max Overclock - 2.1V)
- XFX nForce 780i SLI motherboard
- Intel Core 2 Duo E6750 (8x333MHz);
- Nvidia GeForce 8800 GT 512MB
- Corsair TX750W PSU
- Seagate 7200.10 200GB SATA hard drive
- Windows Vista Home Premium 64-bit
- Nvidia Forceware 169.25
To make the most of the 4GB of memory we've upgraded to use Windows Vista Home Premium x64 which will make use of the entire memory footprint. For those using a 32-bit OS, you'll be limited to 4GB minus other addressable memory in the system. The most notable chunk that will prevent you from reaching the 4GB limit is the graphics card, which can vary in memory size quite a bit. If a typical graphics card has 512MB of memory, you'll still be able to use 3.5GB of memory which is obviously closer than 4GB than 2GB, but you're still not getting the full value of your purchase.
We're using the nForce 780i SLI because it supports EPP and a semi-unlocked memory bus which allows easier memory scaling while keeping a consistent CPU speed in order to keep the results subjective.
As previously mentioned, we found that 2.1V was the sweet spot for both sets of modules, even 2.15V was "too much" and dropped the stability. In fact, only a small tweak to the north bridge voltage and the memory was enough to crank it up quite considerably. We kept the latencies to 5-5-5-15 as we overclocked in order to make it more "meaningful" – after all, there's no point in running at some super high speed if the modules have super lax timings to compensate: there's no performance gain.
We did find that the Crucial Ballistix Tracer Red 4GB did get hot when overclocked heavily – a fan over the top helped quite considerably keep things stable, but we found we the extra cooling didn't affect the Corsair DHX modules at all – they felt cooler to touch, but they sadly didn't overclock nearly as well.