Clock Or Timing Settings?
AData rates its DIMMs at DDR2-800, while Corsair prefers to constrain its ratings to 675 MHz ; either way, timing settings of CL3-2-2-8 will work.
We set up our testing to include both fast and slow timing settings. Our experience with DDR1 memory modules made it clear that attractive timings are often the better choice. For the same reason, AMD plans to delay its adoption of the M2 socket and DDR2 until CeBIT 2006 - its engineers found the benefits of DDR2 at 800 MHz too small to be worth the added expense.
In the meantime, various memory vendors are heading in different directions. AData describes its DDR2 DIMMs as definitely capable of handling 800 MHz, a claim that our limited testing affirms without question. But to attain these rates, timing settings must also be tightened considerably. Corsair takes a different approach : its highest-rated DDR2 memory modules are rated only to a maximum of 675 MHz, but also support optimal timing settings of CL3-2-2-8. This lets Corsair achieve higher performance than vendors that offer DDR2-800 products.
More Power, Less Life
Because production limits won’t yet allow commercial yields for 400 MHz-capable chipsets, higher clock rates will continue to demand higher input voltages as well. DDR1 still requires 2.5V, so overclockers routinely boost voltages to 3.0V and beyond. But for DDR2, base requirements start at 1.8V. This means rates of up to 2.0V aren’t much of a stretch ; even appreciably higher levels aren’t unusual, serving as an earnest topic of discussion in many overclocking forums online.
Raising the input voltage also tends to boost memory tolerances as well : this makes higher clock rates and more aggressive timing settings possible. But the tradeoff is that higher voltages also significantly reduce memory component lifetime.