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DDR3-1600 in Overclocked Systems

The next series of tests will reveal how well the system equipped with DDR3-1600 SDRAM will perform with the FSB frequency increased to 500MHz. Overclocker platforms often work at this or even higher bus frequency, so memory with high bandwidth may turn out exactly what one needs in this case. This overclocking increases the peak processor bus bandwidth to 16 GB/s, which makes the efficient use of dual-channel DDR3-1600 SDRAM potential much more likely.

For our tests we used the same Core 2 Duo E8600 processor overclocked to 4.0GHz. However, we lowered its multiplier and obtained the resulting frequency as 8 x 500MHz.

Note that this FSB frequency increase should be taken more seriously than the previous one to only 400MHz. In this case, the system may only be stable if running on a high-quality mainboard equipped with an advanced chipset North Bridge cooling system. Moreover, you will most likely have to increase the chipset NB voltage and CPU VTT. Nevertheless, many computer enthusiasts overclock their systems with FSB set at 500MHz or even higher. Many mainstream LGA775 processors support relatively low frequency multipliers that do not allow reaching high frequencies with any other overclocking methods. So, 500MHz FSB is not extreme overclocking exotics, but more of a widely spread occurrence that deserves special attention on our part.

The memory tested within this series of experiments was configured as follows:

  • DDR2-1000, 5-5-5-15 timings, Performance Level 10;
  • DDR3-1600, 9-9-9-27 timings, Performance Level 10;
  • DDR3-1600, 8-8-8-24 timings, Performance Level 10;
  • DDR3-1600, 7-7-7-20 timings, Performance Level 9;
  • DDR3-1600, 7-6-6-18 timings, Performance Level 9.

Here I have to point out two things. First, we had to seriously ease the Performance Level North Bridge timing during overclocking with such aggressive FSB frequency increase. To ensure system stability we had to increase it to 9-10. Second, we had to use the test DDR2-1067 SDRAM in a slightly slower DDR2-1000 mode. The reason for that is the fact that existing Intel chipsets do not support any dividers that could help us set the memory frequency at anything closer to 1067MHz. By the way, for same exact reason when we overclock to 450MHz FSB or higher we have to use “synchronous” divider for the memory frequency (when DDR2 frequency equals twice the FSB frequency) for most DDR2 SDRAM modules.

Nevertheless, despite the above mentioned “allowances”, we hope that additional FSB overclocking will have a positive effect on performance.

The measurements taken with the synthetic Everest Ultimate 4.60 benchmark reveal pretty curious occurrence. It is for the first time that any DDR3-1600 SDRAM turns out faster than DDR2 in bandwidth as well as latency. And it means that our earlier suppositions are correct, namely when the processor bus frequency increases significantly over its nominal value, memory speed is of greater importance. This way, there is no doubt that DDR3-1600 is extremely fit for overclocker systems. Now we just have to estimate how significant the gain from this expensive memory will be.

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