I understood "front side bus "??? Maybe not...

[leoblob]

My new system has 2.66 GHz processors and is advertised with a 533MHz front side bus. The memory is DDR266.

During POST, it shows 2.66 GHz, but then it says bus speed = 133, with a 20 multiplier. I go onto Intel's site, use their spec finder, and it says the same exact thing. And, I know that DDR266 memory is really running at 133 with 2 fetches per clock cycle...

So... everything points to a 133 MHz bus... but why does Intel say "533?" What exactly is it that's running at 533?

I looked at the Intel specs for other processors & same thing. The processors with an advertised 800 MHz front side bus are actually running against a 200 MHz bus...

What am I missing here?

[rkawakami]

Here's a good site which explains most everything:

http://www.directron.com/fsbguide.html

The 533Mhz "speed" is based upon a system clock of 133Mhz and with a multiplier of 4 for the quad data-rate memory being used in your system.

edit: Sorry, I should clarify that it is actually the CPU memory data rate that is being multiplied by 4. The memory needs to be operating in dual-channel mode to get the "effective" 533Mhz data rate. Does that make it any clearer? And somebody correct me if I'm wrong, but that's what I remember from a couple of years ago.

[leoblob]

Thank you for the reference. It all makes sense now... but the engineer in me does think it's a bit misleading for the chip manufacturers to advertise these high bus speeds when they really aren't (as fast as stated).

Oh well...

[rkawakami]

Ah, but if you were in marketing then it would make total sense. Bigger numbers are usually better.

[Kyocera]

Ray, great link I had read some of that on another site but not in that great of detail, thanks.

Mike