AMD FSB Question (need technical info)

[Quazar]

I have a question on the FSB speed of the processor of the Athon CPU. As it was explained to me it is a 100mhz FSB that clocks on the rising and falling making it Equivilent to a 200mhz FSB speed.

Or is it 200mhz that clocks on the rising and falling thus making it equivilent to 400mhz.

Also is there a difference between the FSB and the motherboard bus speed. Is the FSB speed locked on the Athlon and you can only over clock by changeing the motherboard busspeed. ECT.

Can someone explain this to me.

[OuTpaTienT]

Should've stopped with your first sentence...that is entirely correct. It uses a 100mhz bus(actual speed) but uses both sides of the clock ticks (same as DDR RAM) to get the data throughput equivilent of a 200mhz bus.

That same bus architechure currently used by the Athlon is entirely capable of speed up to (& maybe more) 200mhz which of course would be equivilent to a 400mhz bus.

And about FSB vs. motherboard bus. Well, a term like "motherboard bus" is just generic speak and slightly less "techy" sounding so it comes in handy when talking to your buddies that are Mac users. http://www.sysopt.com/forum/wink.gif

FSB is the pathway between the CPU and the motherboard's main chipset (and L2 cache on older systems). Of course there's many other buses at work on the motherboard as well...like the memory bus, video sub-sytem bus (AGP bus) and then there's the PCI bus, and let's not forget the ISA bus (it's not quite dead yet).

Whether you can alter an Athlon's FSB has everything to do with the motherboard and NOTHING to do with the Athlon itself. Some of the m/b's do allow for altering the bus speed manually, some don't. But really, that's the beautiful part about the Athlon design. When you overclock the Athlon, that's exactly what you're doing...o/c'ing the Athlon...ONLY. So you don't have to worry about about every single periphrial being o/c friendly.

Ya see, when you have to increase the FSB to overclock (as with Celerons, PIII's, etc.) then you are also overclocking everthing that the FSB controls. And since usually all the other systems buses (AGP, PCI, etc.) are run as fractions of the main FSB, they get o/c'ed too. Essentially, you end up overclocking EVERYTHING in the computer. If (and that's a huge IF) all goes well, this is great. But it's the old "weak link in a chain" theory...if any one of your system devices doesn't function with the overclock, then you're out of luck. Either no o/c, or replace the device and HOPE the new one can handle it.

Sorry to ramble on...any of that help ya understand it better?

[hd581]

So what will the BIOS report the speed as? 100 MHz?

//edit: Also, How does Sandra report the FSB? 100 Mhz, also?

[This message has been edited by hd581 (edited 06-24-2000).]

[OuTpaTienT]

Well, I currently have my Athlon motherboard overclocked to 121mhz. WCPUID (which is a standard in the overclocking community for reporting such things) is reporting my Athlon/500 is running at 606.29Mhz, and it's bus is running at 242.52Mhz.