Well then you need real GWorld RAM, which is impossible to find these days. I got my 4MB SIMMs from an AVID Nubus capture card (targa 2000 Nubus based), which are very hard to find and pretty much leaves the card useless when you take any. I know IIfx RAM doesn't work in my Supermac Thunder/24's but I figured the people on LEM mac would have tried the IIfx RAM if they said it is compatible (I don't own a 8.24GC to know).