well... depends on what you're doing with it...
OS3.9 on an RTG screen ~4MB
TCP/IP stack ~1MB
USB stack ~1MB
other random stuff you like to run:- magic menu, something mui based, yadda yadda +2/4Mb?
and that's before we've even got going.
YAM email client with all the icons? I can't remember, but it's not going to be cheap
so even the basic 16MB on the 3k/4k mobo starts to look limiting.
a little bit of quake for sir/madame? as much ram as you want to assign
PPC based heretic2 wants at least 64MB.
I just like the idea of 128MB+ ram... means you don't worry about it
and 256MB... well, that's just "infinite" as for as miggys go I guess
