DDR3 vs. DDR2Here, we were first of all interested in power consumption on the Gigabyte card, which is able to manage two types of memory. In order to obtain precise figures, we measured the power supplied to the motherboard at its ATX plug with an ammeter. This allows us to eliminate processor consumption and part of the graphic card‘s.
In rest, there is gain of about 2 watts compared to DDR2 (2x1 GB of Corsair PC8500), and this went as high as 5 watts in load (with Prime95). It should be noted, however, that to have equivalent timings we had to increase the DDR3 to 1.8V or the same power consumption as DDR2. Here, consumption was then more than 1 watt in rest and less than 1 watt in load. For a desktop PC, DDR3 doesn’t change much in this area, however, for a laptop it could be of greater consequence.
The P35 Express chipset offers a number of bus processor and DDR3 frequency ratios. Here are the ones available on the P5K and P5K Deluxe :
- FSB1066 : DDR3-800, DDR3-889, DDR3-1067
- FSB1333 : DDR3-800, DDR3-833, DDR3-1000, DDR3-1067, DDR3-1111, DDR3-1333
Let’s now see the performances of DDR3, first with a Core 2 E6750 set at 2.67 GHz in FSB1333 on the P5K and P5K3. We used four measurements; the rate in MB/s and the latency in cycles measured by ScienceMark 2, compression time of files with WinRAR 3.7, and finally, the framerate in Far Cry. These two « practical » applications were chosen because they are noticeably affected by the speed of the memory sub-system, something that isn’t always the case.
The first thing we see is that DDR3-800 in 5-5-5 is slightly slower in terms of latency, as we expected and this places it 1 to 1.5% behind DDR2 in our practical tests. The second observation is that DDR3-1333 only has slightly superior performances than DDR2-1067.
For the latency/frequency combo, we can see that DDR3-1333 CL9 is faster than DDR3-1067 CL7, which is in turn superior to DDR3-800 CL5. In DDR2, the DDR2-1067 CL6 is equivalent to DDR2-800 CL4, while the DDR2-800 CL5 and DDR2-667 CL3 are equal. Finally, if we look at the fastest and slowest memory configurations, there is only a gain of 14% in WinRAR and 10% in Far Cry. Memory does not have as a big an impact on performances as some claim.
Does the gap between DDR2 and DDR3 change with a bigger FSB? To find out, we used a FSB1777 (444 MHz) while keeping a frequency of 2.67 GHz. Here are the results:
Increasing the FSB isn’t in favour of DDR3 and the DDR2-1067 shows an even larger gap. It seems as if the FSB:DRAM ratio of 2:3 used here is less effective than the 1:2 necessary in FSB1333, because despite the increase in bus frequency, application performances stagnate.