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.

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Header Cell - Column 0 Dual Channel PC800 RDRAMPC2700 DDR-SDRAM (DDR333)PC2100 DDR-SDRAM (DDR266)PC1600 DDR-SDRAM (DDR200)PC133 SDRAMPC100 SDRAM
Clock400 MHz166 MHz133 MHz100 MHz133 MHz100 MHz
Differential?Yes 2xYes 2xYes 2xYes 2xNo 1xNo 1x
Bus Width in Bit2 x 16-bit = 32-bit64-bit64-bit64-bit64-bit64-bit
Bus Width in Byte2 x 2 Byte = 4 Byte8 Byte8 Byte8 Byte8 Byte8 Byte
Peak Bandwidth3200 MB/s2666 MB/s2133 MB/s1600 MB/s1066 MB/s800 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.