80000 = error at address 512 KB
From the the information at [
here], the problem is expected to be in the chips that comprise the 128 KB component of motherboard RAM (the blue chips in the diagram).
0000 = no data bits in error, which together with the "PARITY CHECK 1" error suggests a problem with one of the two parity bits.
From the the information at [
here], the problem is expected to be either a faulty U4 or a faulty U1.
But rather than one of the chips being faulty, maybe the problem cause is a poor electrical connection - try reseating U4 and U1.