Methods and apparatus for use with AGP-capable computer systems are disclosed. Since each AGP-capable chipset can have a unique range of graphics port aperture sizes that it supports, current graphics port aperture drivers are chipset-specific, with hard-coded tables of supported graphics aperture sizes. Described herein is a driver that dynamically ascertains the range of supported graphics aperture port sizes for an attached AGP-capable chipset, thus allowing this driver to be ported between different chipsets without manual reconfiguration and recompiling. The method employed in the driver sends one or more test aperture size values to a register resident in the chipset, and then reads what is written to see if the chipset changed any of the bits of the test value. The method infers supported sizes from examining which, if any bits, were changed by the chipset.