How much memory bandwidth can the P4 handle?

[Dug]

Is there a limit on what the cpu will be able to use, or does it scale with the speed of the cpu?

 

[ElFenix]

it needs about 1 MB/MHz

 

[fkloster]

....

 

[CrazySaint]

FSB * 64 / 8 = bandwidth a P4 can handle. For example, take a P4 with a 533MHz FSB. 533 * 64 / 8 = 4264 (4.2GB/s). My P4 1.8A @ 2.7GHz has a 600MHz FSB so 600 * 64 / 8 = 4.8GB/s of bandwidth. Unfortunately, my DDR400 RAM is only supplying about 3GB/s of that, hence the excitement over DC DDR

 

[Dug]

So the bus is the limiting factor? If the bus to the P4 was 1066 then it could handle 8.5GB/s?

If the bus is the limiting factor then DC DDR theoretically supplies the maximum bandwidth a P4 can handle at any speed the CPU is running, because its a 1:1 correlation, correct?

 

[fkloster]

that sounds correct. remember that we are talking about peak/potential bandwidth...not sustained.

 

[Nemesis77]

the speed of the FSB determines the CPU's ability to use the mem-bandwidth. Altrough AMD's Hammer is an exception, since it has integrated mem-controller. In that case the speed is determined by the width and speed of the memory-bus and the speed of the memory (in Clawhammer 64bit @ 333MHz, Opteron 64bitx2 @ 333Mhz)