Viper Series 2GB PC3-12800 DDR3 Memory Kit was installed in a system with the following components for this review:
» Intel Core 2 Duo E6850 Dual Core
» ASUS P5KC P35
» Western Digital Caviar SE16 WD7500AAKS 750GB
» PC Power and Cooling 750 Quad Silencer
» ASUS EAH3850 TOP Overclocked Radeon HD3850
» Ultra Products m998 Mid-Tower
» Windows XP Professional
The module's specifications indicate default timings of 7-7-7-18 at 1600MHz, which are rather tight for DDR3 especially at such an elevated clock speed. The screenshot below was taken from CPU-Z Version 1.44.1 in order to check what the modules had to say about their timings. The "SPD" tab indicates that the modules were programmed for 7-7-7-18 and 1.8V at 1600MHz (the XMP-1600 profile), so no manual adjustment should be required if your BIOS can recognize anything this fast by default. Two other "JEDEC" profiles are provided, which indicate the timings and voltages need to run at the rather standard speed of 1066MHz, and the rather unusual speed of 914MHz.
The initial boot with these modules was completed with the BIOS completely in auto mode, and it defaulted to a speed of 1066MHz as expected. With the speed adjusted to 1600MHz and the timings manually adjusted to match the published specifications, the system booted without issue and CPU-Z was checked once again. The below left screen confirms that the processor was now running at 3.2GHz (8x400MHz) with a 1600MHz FSB, while the below right screen confirms that the 7-7-7-18 timings were achieved at this speed.
Some preliminary benchmarks and a 30 minute session of OCCT
were conducted to confirm system stability, and once satisfied that everything was good to go I moved on to more in depth testing and overclocking.
Overclocking and Optimizing:
The ASUS P5KC motherboard supports both DDR2 and DDR3 which makes it great for testing out both kinds of memory, but I have found that it is a bit temperamental when it comes to overclocking either. 1333MHz memory is the maximum stock DDR3 speed, but I have run other kits up to just above 1600MHz. In general it has required a bit of coaxing, something like an old muscle car that runs great once it gets going, but doesn't always want to turn over. This couldn't have been further from the case with this DDR3 kit. It booted right up at 1600MHz and I was honestly surprised at exactly how "plug and play" this installation was.
While maintaining the stock 7-7-7-18 timings at 1.8V I decided to see how high the system would go. Things started to get sketchy as I approached 1650MHz, so I backed down to 1640MHz and called that the maximum overclock without having to loosen any timings or add more voltage. The images below take a look at the CPU-Z tabs in this condition.
To go any higher I had to loosen the timings significantly, and I added an extra 0.2V for good measure. With 9-9-9-25 timings I was able to get to 1680MHz, but a few quick benches showed that the effort wasn't really worth it. I was better off back at 1600MHz and stock timings according to Everest Ultimate Edition.
In all honesty I can not say that the memory limited the overclock, as this is a 1333MHz FSB processor that was now running at 1680MHz! There just aren't any more memory dividers left on this board to eliminate the CPU from the equation.