PC133 SDRAM is just about the same as PC100 SDRAM except for the bus speed is 133 MHz instead of 100 MHz. That is about one third faster. A CAS latency of 2 is pretty much standard for most PC133 memory. Memory with a CAS 3 latency is a few per cent slower than CAS 2 memory. PC 2100 is the DDR (double data rate) version of PC133. PC1600 is the DDR version of PC100. PC2100 is only a few dollars more than PC1600 so it gives you the most value for your money, even if you are going to put it with a motherboard and CPU with a front side bus speed of 200 MHz for now. The effective speed of double data rate PC2100's 133 MHz clock is 266MHz because data is transfered on both the rising edge and the falling edge of the 133 MHz clock. As far as RDRAM goes, just say NO. The only way to get any real speed out of RDRAM is to use a bank of four modules. As if they wern't expensive enough one at a time. The latency of RDRAM is so horribly long that in most stuations it more than eats up any clock speed advantage. One of the worst features of RDRAM is that it can only transfer 16 bits at a time (16 bits = two 8 bit data Bytes). SDRAM transfers data in blocks of 64 bits at a time (64 bits = eight 8 bit data Bytes). So when they jump up and down about the effective speed of 800MHz RDRAM that only means a peak data transfer rate of 1600 MB/s, that is 800 MHz times 2 Bytes at a time. The term PC2100 comes from the peak data rate of 2100 MB/s, or 266 MHz times 8 Bytes = 2128MB/s A CAS latency of 2.5 is the usual for both PC2100 and PC1600 SDRAM PC100 and PC133 both use the same old 168 pin SDRAM socket. PC2100 and PC1600 SDRAM have 184 pins. RDRAM uses RIMM sockets. Have fun!
What motherboard is it?
