AGP clock speed question.

[PDL]

I am running an ATI Rage 128 card and it is set to 1x in bios.
When I begin to raise the FSB I get a change in the speed that I don't understand.
At FSB of 121 the AGP speed is 60 MHz.
Dropping the FSB back to 120, the speed changes to 80 MHz.
This is as reported by SiSoft Sandra 2001te Standard.
BTW, this is also the point at which the PCI divisor changes from 1/3 to 1/4.
Continuing on up from 121, I have raised the FSB all the way up to 166 and the AGP speed just keeps going up as well, up to 84 MHz.
It hits 80 MHz again at FSB of 158.
Anyone know why the change at 120 or is this a flaw in the Sandra report?

[Pinky]

Originally posted by dad
I am running an ATI Rage 128 card and it is set to 1x in bios.
When I begin to raise the FSB I get a change in the speed that I don't understand.
At FSB of 121 the AGP speed is 60 MHz.
Dropping the FSB back to 120, the speed changes to 80 MHz.
This is as reported by SiSoft Sandra 2001te Standard.
BTW, this is also the point at which the PCI divisor changes from 1/3 to 1/4.
Continuing on up from 121, I have raised the FSB all the way up to 166 and the AGP speed just keeps going up as well, up to 84 MHz.
It hits 80 MHz again at FSB of 158.
Anyone know why the change at 120 or is this a flaw in the Sandra report?

The AGP clock/divider is usually in conjunction with the PCI/bus.

When you're running at the PCI of 1/3, your agp is set to 2/3... en you jump to 1/4, AGP changes to 1/2

Mathmatically: PCI=33mhz (best speed)
AGP=66mhz (best speed)