What's the difference between FSB & Memory bus?

[John]

I can run 142 FSB / 142 Memory bus on my A7V133. However I cannot run anything above it. I can run 120 FSB / 160 Memory bus too and my memory scores are that of DDR's (585/711). What's the difference?

PCI bus is 35.5MHz @ 142 & 40MHz @ 120.....

 

[AndyHui]

On chipsets and motherboards where the memory cannot run asynchronously from the FSB, then nothing. Otherwise, FSB is the speed at which the motherboard runs at, and from that the PCI and AGP buses, while the memory bus is only linked, usually with a +/- 33MHz...ie the RAM runs at a different speed to the motherboard.

In your case, you run the motherboard a little slower, and your RAM faster, at the possible expense of stability. I really recommend avoiding a PCI bus speed of 40MHz.

SANDRA memory scores are not the final word on performance....I'd rather have the 142MHz FSB and Memory bus.

 

[soulm4tter]

The System Bus is the speed at which the chipset (VIA 8363A North Bridge) can send and receive data from the CPU and Memory.

While the Memory Bus is the speed at which the Memory and send and recieve data from the CPU itself.

The Chipset will send a request to memory for some info and then the Memory Bus will be used to transport said data. So the System Bus is used for the requests of data and commands while the Memory Bus is used for the actual movement of data.

 

[nortexoid]

1, u're running them synchronously, 2, u're running them asynchronously...

the front side bus is the external clock that the internal peripherals operate at....
the memory frequency is the clock the memory operates at.

u can't run them asynchronously over 133mhz on a kt133a...or so i thought...
which is why i'm wondering how u're running 120/160....and why your pci/clock ratio changes from 2/4 in 1, but stays at 2/3 in 2...does it do it automatically?...

 

[John]

Thanks for the clarification guys. I am not concerned w/ a 40MHz PCI bus since I know my components will handle it. Since I can run 120/160 my PCI stays 1/3. If I got to 121+ it goes to 1/4.