DDR333
Maybe not every one of you is familiar with the term 'DDR333'. There have been too many different names for DDR-memory so far. The new double data rate memory supported by SiS645 is clocked at 333 MHz vs. the 266 MHz of the fastest DDR-DIMMs so far. DDR266 is also known as PC2100 memory, which comes from the fact that DDR-SDRAM provides a bandwidth of up to 2133 MB/s. DDR333 could therefore also be called PC2700, as its peak bandwidth is 2666 MB/s.
| Header Cell - Column 0 | Dual Channel PC800 RDRAM | PC2700 DDR-SDRAM (DDR333) | PC2100 DDR-SDRAM (DDR266) | PC1600 DDR-SDRAM (DDR200) | PC133 SDRAM | PC100 SDRAM |
|---|---|---|---|---|---|---|
| Clock | 400 MHz | 166 MHz | 133 MHz | 100 MHz | 133 MHz | 100 MHz |
| Differential? | Yes 2x | Yes 2x | Yes 2x | Yes 2x | No 1x | No 1x |
| Bus Width in Bit | 2 x 16-bit = 32-bit | 64-bit | 64-bit | 64-bit | 64-bit | 64-bit |
| Bus Width in Byte | 2 x 2 Byte = 4 Byte | 8 Byte | 8 Byte | 8 Byte | 8 Byte | 8 Byte |
| Peak Bandwidth | 3200 MB/s | 2666 MB/s | 2133 MB/s | 1600 MB/s | 1066 MB/s | 800 MB/s |
You can easily see that dual-channel RDRAM, as found in Intel's 850 Pentium 4 chipset, is still providing the highest bandwidth. However, DDR333 is pretty close and coming with 25% more bandwidth than DDR266/PC2100 DDR-SDRAM. All SDRAM types benefit from a lower latency than RDRAM, which can make up for lower bandwidth in the majority of today's applications.
