Raising FSB. Why don't peripherals explode?

[dgk]

There is a thread (FSB Better Than Higher Mult) that reminded me of an earlier thread concerning drives screwing up at high FSBs. Upping the CPU multiplier doesn't muck with anything but the CPU. Upping the FSB mucks with everything on the bus.

Do peripherals base their internal workings on the bus speed? Clearly sound cards don't, or music would sound like the Chipmonks. Drives, I think do.

So, if a drive is rated at 7200 rpm, clearly the speed doesn't vary when the FSB is increased. Does the transfer rate? Does it depend on using DMA or whatever other access methods are used?

Video cards have their own tweaking programs, so OCing those doesn't depend on the FSB.

Well, how do peripherals react to FSB changes?

[wild_andy_c]

The internal clock of a peripheral will be governed by the Bus it runs on, just as the internal clock of a processor is governed by the clock that it runs on - the FSB.

[Yomama]

The issue at hand is the PCI bus speed that is specified to be 33.33 MHz or 1/2 of 66.66, or 1/3 of 100MHz or 1/4 of 133.33MHz. The fractions here are the PCI dividers, and depending on motherboard, they usually kick in when the PCI bus reaches about 40MHz.

This had been an issue a number of years back, when people were trying to o/c 66MHz cpus to 100MHz, but could only reach 83 (=41.5MHzPCI) a then typical value between 66 and 100.

Now there are a few devices that cannot handle anything high (e.g. above 36 MHz). Most notably these are network cards, and most annoyingly - because of the consequences - there are some harddrives (e.g. some of the otherwise good Maxtor drives) that cannot handle higher PCI speeds.

This issue was mostly gone with the introduction of the 1/4 divider at 133, but is resurfacing, as people now reach speeds above 150MHz.

Yo

[dgk]

Oh. So the PCI bus speed should be 33 but can go up to 40. The speed is then a ratio of the FSB. As the FSB goes up, the PCI bus goes up. To a certain point, then the next ratio kicks in and knocks it back down. So the idea would be to get the PCI bus running as fast as it can before getting knocked back down.

Memory runs at the speed of the front side bus? But the A7V (and other mbs I guess) adjusts the speed of memory directly (7 or 8 ns?)?