DDR2-667 Is Coming!
You can read about the basics of DDR2 memory here . DDR2 is the successor to conventional double data rate SDRAM, but does not introduce any really new technology. Data is transmitted both at the rising and the falling clock edge, which results in a doubling of bandwidth. DDR2-533 works at a basic clock of 266 MHz. Multiplying by its bus width of 64 bits will give you the bandwidth in Megabits per second. Dividing by 8 will result in MegaBytes per second. The following table includes all common DDR memory types:
| Memory | Clock | Type | BandwidthSingle Ch. | BandwidthDual Ch. |
|---|---|---|---|---|
| DDR266 | 133 MHz DDR | PC2100 | 2,100 MB/s | 4,200 MB/s |
| DDR333 | 166 MHz DDR | PC2700 | 2,700 MB/s | 5,400 MB/s |
| DDR400 | 200 MHz DDR | PC3200 | 3,200 MB/s | 6,400 MB/s |
| DDR2-400 | 200 MHz DDR | PC2-3200 | 3,200 MB/s | 6,400 MB/s |
| DDR2-533 | 266 MHz DDR | PC2-4300 | 4,266 MB/s | 8,533 MB/s |
| DDR2-667 | 333 MHz DDR | PC2-5300 | 5,333 MB/s | 10,666 MB/s |
| DDR2-800 | 400 MHz DDR | PC2-6400 | 6,400 MB/s | 12,800 MB/s |
The credo of DDR2 memory is to increase the clock speed in order to get more bandwidth - even with reduced timings. CL4-4-4-12 are typical timings for DDR2-533, while the JEDEC only specifies CL5-5-5-15 for the higher speed grades. All three DDR2 memory types we received by now are able to run DDR2-700 (350 MHz) at CL4-4-4-12. Crucial does even allow for CL4-4-4-10.
