The Best Thing That Could Happen To Intel's Pentium 4 - The SiS645 Chipset


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.

  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.

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