Update with the ACA 1220@25 MHz. I tested this card in my ACA 500 for a whole day at a Commodore meeting in The Netherlands and didn't crash.
When I set the 1 MB Chip on both A500 rev.6 and rev.8 with the ACA 500, I get an error message that I haven't enough Chip memory in WHDLoad 17.2. I tried to run Mortal Kombat and Sleepwalker.
Do I need to modify those motherboards?