Clarification needed on FSB speeds

[mattschaller]

Hi,

I have a question about FSB speeds.

I know FSBs range between 266 and 500 nowadays, with 500 being the extreme upper limit. Meanwhile I hear people talking about how their FSB is running at 1333MHz, 1600MHz, etc... is this because the FSB is quad pumping data per clock cycle? Because of the chipset's 4 64-bit wide buses, right? I could be getting this wrong.

I just wonder why motherboards say that they are 1333MHz capable or whatever, unless they really are?

Also, when the memory divider is set at 1:1 (FSB:memory) I'm assuming that it is being divided against the 1064MHz/1333MHz/1600MHz number, right? I've just been multiplying the bus speed (266/333/400) by two to find out how fast my memory will run...

If anyone can clarify this for me, that'd be great.

Matt

 

[f4phantom2500]

yup, traditionally it's via a multiplier like that. on amd's htt the htt has its own multiplier that results in its frequency (200x2x5=2000) x2 is always there i think because its ddr. intels 1333 is really quad pumped 333, 800 is 200, etc. if you go into the bios and the fsb setting you'll actually see the base number.

 

[tersome]

1333mhz, 1600mhz etc is pretty much all marketspeak. The memory divider is usually multiplied by the base number. 1:1 with a 333mhz FSB would give you 333mhz ram speed.

Of course, the memory is "double data rate", so you have to multiply that number by two to get the "actual" ram speed.

 

[jackwhitter]

actual board clock rate is 333 fsb, but it transfers 4 times per clock cycle, thus 1333 fsb on the cpu. the ram used is all double data ram (2 times per clock cycle), so you need ddr ram that is clocked at ddr 667 to get a matching base rate for a 1:1 ratio.