Re: 6502 illegal opcodes questions

[Bruce Tomlin <bruce#fanboy.net@127.0.0.1>]

In article <d4CdnR_y__CUmfXZnZ2dnUVZ_s-dnZ2d@comcast.com>,
 "Michael J. Mahon" <mjmahon@aol.com> wrote:

> True, but the decoding in the 6502 is handled by a kind of PLA, so
> it would likely not be very expensive (in real estate) to trap or
> NOP the invalid combinations.

Nope, it's handled by good old random logic.  A PLA is designed to be a 
programmable generic replacement for random logic, and is way too 
inefficient for high-volume VLSI.