Date   : Fri, 02 Sep 1994 15:39:14 +0100
From   : D.LODGE@...
Subject: Re: UNDEFINED 6502 OPCODES

>umm, you could be right. when trying to run zalaga on my beeb emulator, it
>bombs out with an invalid opcode - &EC i believe. i'm not saying my emulator
>is without fault (heaven forbid) but it IS suspicious because other games
>are running flawlessly.

The reason is that on Zalaga, Orlando (the programmer) decided to trap the
unknown instruction (? - I've been programming ARM for too long :) vector and
use it to redefine some opcodes which I believe are on the 65c02 - if the
emulator can't emulate this vector trapping then Zalaga won't run...

Note: Zalaga runs on my Arc Beeb Emulator

d