Stock Memory Performance
Most Intel Socket T (Socket 775) motherboards provide a wide range of memory ratios that match available DDR2 memory. End-users can select the memory ratio that matches their DDR2 memory speed. Our memory testing begins with the same approach. We first test all of the stock ratios at the fastest stable timings we can achieve at the given ratio. With ratios, CPU speed remains the same at 2.93GHz in our memory test bed, and memory speed is varied by selecting different ratios.
There are some downsides to this approach. With the memory controller in the chipset, instead of part of the processor as in AM2 systems, there is a small performance penalty for speeds other than a 1:1 ratio (DDR2-533 in this case). The performance penalty is actually very small and has minimal impact on test results. As a result memory scales nicely through the various speed options.
DDR2 memory is then pushed from the highest stock ratio that could be achieved in testing - in this case 1067 - to the highest FSB speed at the stock multiplier. In the case of the G.Skill DDR2-800 speeds higher than DDR2-1067 were not completely stable. While we could boot as high as DDR2-1100 we could not complete our memory benchmarks at speeds above DDR2-1067 with the maximum 2.4V available on the ASUS P5W-DH. Boards with an extended top voltage range, like the DFI 590 for AM2, may be able to squeeze even more performance from these G.Skill DIMMs.
It is also worth pointing out that two sets of DDR2-800 benchmarks were run. The G.Skill memory required more voltage than the more expensive Micron D9 chips to perform with stability at 3-3-3 DDR2-800 timings. The great news is that they could match the fast 3-3-3 timings we have seen on other Micron D9, but they required 2.35V to do this, where the more normal required voltage is 2.2V.
Many buyers of mid-range DDR2-800 memory will not have a high-end motherboard that can supply voltages like 2.35V in their system. For that reason we also tested the specified 4-4-4 timings at DDR2-800. Those results were a very pleasant surprise since we achieved stability with just 1.9V at 4-4-4-12 timings. This is a voltage that any Core 2 Duo or AM2 motherboard should be able to deliver.
You can also see that 2.35V was required to reach stable performance at DDR2-1067. The good news is that the G.Skill DDR2-800 can be overclocked to DDR2-1067, but you will need voltage to reach that overclock. While we did not include results in the chart we did try to see how far we could push the G.Skill with 5-5-5-15 timings and a more modest 2.0V. The memory remained stable to just above DDR2-1000 at 2.0V.
This performance pattern gives most every buyer some choices when using this G.Skill DDR2-800 in their system. If their board is voltage limited, the memory is still usable at slightly slower timings. If the board supplies a very wide voltage range, then you can likely squeeze even better timings from this memory with higher voltage.
Most Intel Socket T (Socket 775) motherboards provide a wide range of memory ratios that match available DDR2 memory. End-users can select the memory ratio that matches their DDR2 memory speed. Our memory testing begins with the same approach. We first test all of the stock ratios at the fastest stable timings we can achieve at the given ratio. With ratios, CPU speed remains the same at 2.93GHz in our memory test bed, and memory speed is varied by selecting different ratios.
There are some downsides to this approach. With the memory controller in the chipset, instead of part of the processor as in AM2 systems, there is a small performance penalty for speeds other than a 1:1 ratio (DDR2-533 in this case). The performance penalty is actually very small and has minimal impact on test results. As a result memory scales nicely through the various speed options.
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| Click to enlarge |
DDR2 memory is then pushed from the highest stock ratio that could be achieved in testing - in this case 1067 - to the highest FSB speed at the stock multiplier. In the case of the G.Skill DDR2-800 speeds higher than DDR2-1067 were not completely stable. While we could boot as high as DDR2-1100 we could not complete our memory benchmarks at speeds above DDR2-1067 with the maximum 2.4V available on the ASUS P5W-DH. Boards with an extended top voltage range, like the DFI 590 for AM2, may be able to squeeze even more performance from these G.Skill DIMMs.
It is also worth pointing out that two sets of DDR2-800 benchmarks were run. The G.Skill memory required more voltage than the more expensive Micron D9 chips to perform with stability at 3-3-3 DDR2-800 timings. The great news is that they could match the fast 3-3-3 timings we have seen on other Micron D9, but they required 2.35V to do this, where the more normal required voltage is 2.2V.
Many buyers of mid-range DDR2-800 memory will not have a high-end motherboard that can supply voltages like 2.35V in their system. For that reason we also tested the specified 4-4-4 timings at DDR2-800. Those results were a very pleasant surprise since we achieved stability with just 1.9V at 4-4-4-12 timings. This is a voltage that any Core 2 Duo or AM2 motherboard should be able to deliver.
You can also see that 2.35V was required to reach stable performance at DDR2-1067. The good news is that the G.Skill DDR2-800 can be overclocked to DDR2-1067, but you will need voltage to reach that overclock. While we did not include results in the chart we did try to see how far we could push the G.Skill with 5-5-5-15 timings and a more modest 2.0V. The memory remained stable to just above DDR2-1000 at 2.0V.
This performance pattern gives most every buyer some choices when using this G.Skill DDR2-800 in their system. If their board is voltage limited, the memory is still usable at slightly slower timings. If the board supplies a very wide voltage range, then you can likely squeeze even better timings from this memory with higher voltage.
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Wesley Fink - Friday, November 3, 2006 - link
Yes, you can use dividers in overclocking. The ratios and underlying frequencies are more complicated than they appear on the surface, but we have shown in numerous memory reviews that the penalty for not running the preferred 1:1 is really pretty small.If cost is a constraint in a build then money put in a video upgrade first will deliver the most improvement in performance, a CPU would be the next place the upgrade yields great value. Higher memory speeds do increase performnace, but the increases are very small compared to a video card upgrade or a CPU upgrade.
Madellga - Saturday, November 4, 2006 - link
How do you run the memory slower?This was an option with the A64, but so far with the 965 chipset the options are to run the the memory faster, not slower.
My sample size is small, but both the Abit AW9D (975) and Gigabyte DS4 (965) don't have ratios to slow down the memory.
Wesley Fink - Saturday, November 4, 2006 - link
The memory may be RATED at DDR2-800, but you can select memory ratios to run the base at DDR2-400, 533, 667, 800, 1066 and sometimes in-between ratios. That allows you to set the memory at DDR2-400, for example, and overclock your CPU to much higher levels. This is how we test memory at different speeds. This feature is also available on almost every 975, 965, and AM2 board we have tested - except the very lowest models.For example, if I set my DDR2-800 to DDR2-533 (1:1 ratio) I can overclock my bus to 1600 (400 FSB) and then be at the specifed speed of DDR2-800. Remember the bus is quad-pumped on Intel - 266 is the base setting for 1067. Memory is DOUBLE dat tate, so DDR2-533 is a base setting of 266 - that is whay it is 1:1. So at a 400 setting bus speed is 1600 and memory is DDR2-800.
Madellga - Sunday, November 5, 2006 - link
Wes, thanks for the explanation. I've always used 1:1, when you mentioned using dividers I thought you meant something under 1:1.The A64 "dividers" were less confusing than Intel's memory straps, despite the fact how the divider was calculated.
vailr - Friday, November 3, 2006 - link
Any thought of running the memory tests under Windows XP x64? Do the Sandra benchmark tests run in the x64 operating system?Gary Key - Friday, November 3, 2006 - link
The Sandra benchmarks will run fine in XP-64. Once VISTA goes is RTM then we will be switching over to this OS. We had thought about doing some XP-64 tests when Conroe launched but decided to wait (and wait and wait and wait as it turns out) for VISTA.vailr - Friday, November 3, 2006 - link
Vista will also be offered in x64 and "x86" versions. Which version will be favored, as far as AT reviews & benchmark tests?Wesley Fink - Friday, November 3, 2006 - link
64-bit Vista is touted as the PRO version, with 32-bit Vista more akin to XP Home. Unless there are strong reasons otherwise the 64-bit version will likely be the standard.MxChris - Friday, November 3, 2006 - link
How is this different from this set: http://www.newegg.com/Product/Product.asp?Item=N82...">F2-6400CL4D-2GBPK that I bought a coule months ago? Looks to have exactly the same rated timings and specs according to newegg.Wesley Fink - Friday, November 3, 2006 - link
According to G. Skill specs, your memory is rated 1.9-2.0V at 4-4-4-12 and it is pictured with a pale blue heatspreader. Our test dimms are rated 2.0-2.1V for the same timings and have black heatspreaders. You will need to ask G. Skill if your dimms use different memory chips since we don't have samples available to check the chips used on your model number.Your G. Skill kit is curently selling for $240 at newegg compared to $299 for the kit we tested, so I suspect they are based on different memory chips. The Micron chips are notoriously expensive - even with slower bins -and we have seen Mosel used in some mid memory of late, as well as the Elpida that is normal for low-mid memory.