the initial state of the ppu is Vbank nmi OFF, it must be selected. smb should run with no ppu support other then flag setting and NMI's. if it is still crashing, I'd say it's a cpu problem, try to get mario to run without crashing before you play with the ppu. check your PC incriments, this will cause games to crash more then flag problems. most branches are to valid code so if you're getting lots of invalid instructions durring execution, you could be adding the wrong number to the PC after an instruction. if your flags are wrong, the branches would just branch to wrong locations, but the thing shouldn't be executing invalid op codes, unless they are using function pointers or something. is smb working for you??