disable that one for sure

it is only to modulate the clock so that the FCC picks up only a fraction of the EMI at a narrow measuring window..

On the BX chipset, the AGP divider was tied to the bus frequency and the "B21" signal on the CPU that signalled whether the CPU was a Celeron (in that case, the AGP divider was 1/1) or else a Pentium (in that case, the divider was 2/3)

I never used a Celery on that board, but you might want to check the BIOS for a setting of the AGP frequency.