Today we're going to examine how different memory frequencies, timings, and configurations affect the memory bandwidth and real performance of Core i7 processors. This is especially important so that you can not only get the best out of your Core i7 CPU, but also potentially save a lot of money.
Finally, it is possible to configure a Core i7 processor with three-channel memory that works at 1066, 1333 and 1600 MHz or even faster. But what are the advantages of more aggressive clocked storage?
In the past, when testing the Core 2 processor family, we found that spending more money on high-speed DDR2 and DDR3 memory is a real waste of money because the processor couldn't use the extra bandwidth.
While previous Intel processors such as Core 2, Pentium D, Pentium 4 etc. had to rely on the Front Side Bus (FSB) to access RAM, this was not the case with the new Core i7 processors. The Intel FSB, which was used on the Core 2 motherboards, enabled 4 transfers per clock, which Intel referred to in marketing as the "Quad-Pumped Front Side Bus".
This meant that the Core 2 Duo E8500 processor running on a 333 MHz FSB could do 1333 million transfers per second. Since this FSB was 64 bits wide, the end result was a bandwidth of only 10.6 GB / s (1333 x 8). This is Intel's problem. Your current 333 MHz FSB supports a maximum memory bandwidth of only 10.6 GB / s, which is exceeded by the DDR2-800 memory in two-channel mode.
We have known for some time that DDR2-1066 for Core 2 users does not offer a significant performance gain over DDR2-800 memory, since DDR2-1066 memory in dual-channel mode offers a peak bandwidth of 17 GB / s, which is far above the 10, 6 GB / s limitation of the 333 MHz FSB.
Then came the DDR3 memory standard, which in principle works similarly to the DDR2 memory, only at much higher frequencies. Again, DDR3 had little impact even when compared to DDR2 memory at just 800 MHz. Just like the faster DDR2-1066 memory, DDR3-1333 offers a peak bandwidth of 21.3 GB / s, while DDR3-1600 reaches 25.6 GB / s, both of which are the 10.6 GB / s limit of 333 MHz -Exceed FSB for miles.
This is the reason why DDR3 didn't get going. But with the new Core i7 platform, DDR3 should finally get the chance to shine. As already mentioned, the Core i7 has an on-die memory controller with support for three-channel DDR3 memory. In other words, three DDR3-1333 modules working together offer a peak bandwidth of 32 GB / s, which corresponds to the L2 cache performance of a Core 2 Quad Q6600 processor.
If you're wondering how the FSB can handle three-channel memory if it can't even handle two-channel memory, the answer is simple, isn't it? By using an integrated memory controller (IMC), Intel was able to abolish the old FSB.
How do the Core i7 processors deal with the additional memory bandwidth? Is it used well or is it just wasted like the Core 2 processors? We want to find out, and as we test a range of frequencies and timings, we'll also examine how single, dual, and tri-channel memories affect the performance of the Core i7 processors.