Bios or chipset multipliers?

[KillerBug]

I was wondering...does the bios or the chipset lock the multipliers between 2x and 8x (I don't mean like a P3 450 is 4.5x, like that those are the only available ones), places couls do some major tests of the bus abilities in some of these new boards if they could drop the multiplier on an old .35 micron P2 down to like 1, and test FSBs all the way up to 333mhz before they even overclocked the chip, you would know how stable the board realy is at the speeds no one can even go near, and the only modification might be a small bios modification.

[RobRich]

Someon correct me if I'm wrong, but that is a function of the chipset. The cpu itself is a very limiting factor. The fsb is how fast the chip communicates to the chipset. While today's cpu's can easily operate at higher internal speeds via the clock multiplier, they lack the ability to attain high external transfer speeds.

The ideal approach would be to run the m/b, cpu, and memory at the same clock rate. Think of a 600mhz m/b, with a 600mhz cpu, with 600mhz memory. Throughput would really only be limited to the external bus's, like pci and agp. But hopefully by the time anything like this happens, system devices will be able to communicate with the chipset at the fsb speed.

[This message has been edited by RobRich (edited 10-31-1999).]

[Peter M]

Hi,

the frequency multiplying is done INSIDE THE PROCESSOR, not by the chipset and not by the BIOS.

All the mainboard has to do is provide the base (front side bus) frequency, and set a series of input pins to High or Low level at system reset. These pin's settings are used by the processor to fire up its internal multiplier at a certain rate. Mainboard designers can choose to do this by jumpers, or by some software adjustable circuitry.

It's been that way ever since clock-multiplied processors with adjustable rate are around, which is the 486DX4. Only recently Intel brought us processors that have their multiplier circuitry locked to one single factor, ignoring the setting from outside.

Regards, Peter

[800XL]

The CPU has a set range of multipliers and nothing the chipset or BIOS does can change that. Even an unlocked CPU can only be set to a multiplier that is in its internal table of possible settings. Assuming we are talking about an unlocked CPU, 486DX2/66 to current the CPU reads pins on the motherboard which tell it which multiplier to run at.