Am Montag, 5. September 2022, 15:51:20 CEST schrieb Rainer Buchty: > On Sun, 4 Sep 2022, Gerrit Heitsch wrote: > > But would that also cover the illegal Opcodes correctly? From what I > > understand, those are side effects of the NMOS implementation. > > Were they? I always considered them to be a side-effect of the internal > decoder matrix which did not specifically "NOP" the unused opcodes > (which IIRC was done with the CMOS versions), but just bluntly decoded > the individual parts of the opcode, generating corresponding enable > signals. > > So stuff happened like e.g. loading the accumulator, but also throwing > the X register onto the internal data bus. That is true for most of them. However there are a few (5) opcodes who show behaviour that can not be fully explained that way (shy/sha/shx/ane/lax#imm) - that is also the reason for why those do not work correctly in visual6502. -- http://hitmen.eu http://ar.pokefinder.org http://vice-emu.sourceforge.net http://magicdisk.untergrund.net The question of whether a computer can think is no more interesting than the question of whether a submarine can swim. <Edsgar W. Dijkstra>Received on 2022-09-05 17:03:48
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