Update: I've got opcodes 0x1[JP addr], 0x2[CALL], 0x6[LD], 0x7[ADD], and 0xB[JP addr + v0] working, more or less, as far as I can tell, so I'm pleased. Still no graphics obviously[I have the emulator in a console app for now, so I can easily see the output without having to mess with SDL text rendering].