A2000 Rev 6.2 only showing 512k of RAM

[amiga-penn-wchester]

I have an A2000 + video toaster + C=68030 accel, which originally had normal agnus.   When I added a 1MB agnus from an A500, I had still 512k chip. I had to change a jumper and cut a solder bridge.  Might check into how the accel is autoconfiguring the memory, check the amiga hardware database for jumper settings on your particular accel, or - yes - try another / reseat 1mb Agnus if you can.

[amiga-penn-wchester]

Ah, missed that part above about removing the accelerator. The only things I can think of would be 1) agnus tight in the socket, 2) replace if you can.  Have you looked at a CLI and do 'avail' to see what it reports?  In other words is the extra 512 not addressed by agnus showing up as "other memory" (fast+slow) = 12.5meg, or is the extra 512k just "not there"