Test System, Memory Benchmarks

Test System Specifications
Intel Pentium D 950
Intel Core 2 Duo E6300
Intel Core 2 Duo E6400
Intel Core 2 Duo E6600
Intel Core 2 Duo E6700

Corsair PC5400 Pro 2GB DDR2
Gigabyte 965P-DQ6 (Intel P965)
Seagate 250GB 7200RPM (Serial ATA II)
ASUS Radeon X1900XT (512MB)
- WinXP 32bit - Microsoft Windows XP Pro (SP2)
- NVIDIA Forceware 91.31
- Intel System Drivers 7.2.2

As you can see from the SiSoft2007 memory results each time the Core 2 Duo drops ~270MHz, roughly 50~80MB/s of memory bandwidth is lost. This is not a lot and should not really hurt the lower Core 2 Duo processors that much.

The same performance trends are found in PCmark2005, which also looks at raw memory performance. The MemTach analyze test results are slightly more interesting as bigger jumps are seen between CPUs. Take the Analyze 1 test results for example, the E6600 is 10% slower than the E6700. Where as the E6400 is 12% slower than the E6600 and the E6300 is 14% slower than the E6400.