I have a PowerBook 5300c with 1MB VRAM, and I think one of the VRAM chips is faulty. I get random screen artifacts and MacTest Pro fails the VRAM test (within a localized range e.g. $6000020C, $600126F8, $60013600). I'd like to pry off the offending chip (don't mind 512k VRAM) but how do I identify which one it is, based on the addresses that have failed?