bandwidth question

How do they reach the figures for processor bandwidth (ie like 4.2 GB/s for the P4 at 533MHz)

Is it 133 MHz * 32 bits = 4.256 Gbps ?

If so, then how does the quad pumping help the bandwidth?
Also, if the Athlon processors (133 MHz) have a bandwidth of 2.1 GBps, then what is the need for dual channel memory, when only PC2100 will be sufficient.

I think that DDR for athlon and Quadrate for Pentium determines the final bandwidth (since the P4's is twice that of the athlon) but am unsure how.

Thanks for your help.


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AMD Athlon XP 1700+ | Gigabyte GA-7VRXP | 256 MB PC2700 Nanya | MSI GF4Ti4400 | Seagate Barracuda ATAIV 40GB | Creative Soundblaster Live! 5.1 |

Actually the bus is 64 bits wide or 8 bytes.

So 133 Mhz * 8 (for 64 bits) * 4 (for quad pumped) = 4.256 GB/sec.

For Athlon (266) it's similar.

133 Mhz * 8 * 2 (for double data rate) = 2.128 GB/sec

And, yes, dual channel is overkill for an Athlon. You can't utilize the theoretical bandwidth of 4.2 GB/sec for of dual channel, PC2100 memory when FSB only has a bandwidth of 2.1 GB/sec.

The only gains you get are due to lower latencies which does improve performance a little.

<b>99% is great, unless you are talking about system stability</b>