q4kx@vax5.cit.cornell.edu (Joel Sumner) (03/04/91)
I saw this in alt.folklore.computers and thought it would be interesting. Have fun... -------------------------------- In article <462@rc6.urc.tue.nl>, wsbusup@eutws1.win.tue.nl (Jan Stout) writes: > In a recent posting someone asked for a lists of these, so I'll tell you > what I know... > > The most usefull group of these illegal opcodes execute the 2 instructions > having an opcode 1 & 2 lower, after another. > > For example: > ORA follows ASL so the opcode following ASL executes first ASL then ORA (SLO) > > A list of new mnemonics that operate this way: > > AAX (STA STX) > DCP (DEC CMP) > ISC (INC SBC) > LAX (LDA LDX) > RLA (ROL AND) > RRA (ROR ADC) > SLO (ASL ORA) > SRE (LSR EOR) > > Note that - AAX stores not the A, not the X but the A AND X. > - not all addressing modes are supported (notably not immediate) > > Further opcodes that are not documented either stop execution (KIL) > or skip the next 0, 1, or 2 bytes (NOP, DOP, TOP). > Finally there are a few codes with very exotic behaviour, but > they seem not that usefull. > > More on this topic has been written in a german mag C64er. > I even remember a dutch assembler (CD labelassembler), that knew 7 of the > above mentioned opcodes. > > Jan Stout, wsbusup@eutws1.win.tue.nl -- Joel Sumner GENIE:JOEL.SUMNER This .sig may not be used q4kx@cornella.ccs.cornell.edu q4kx@cornella for public viewing or q4kx@vax5.cit.cornell.edu q4kx@crnlvax5 rebroadcast without the .................................................... express written consent The impedance of absolutely nothing is 377 ohms. of major league baseball.