Re: 6502 illegal opcodes questions

[Eric Smith <eric@brouhaha.com>]

"Michael J. Mahon" <mjmahon@aol.com> writes:
> The 6502 was already a much less expensive processor than its
> competitors, because of a mask retouching technique MOS Technology
> developed that saved mask iterations.

I saw that claim on Wikipedia.  Is there any published reference?

Stephen Harris wrote:
> With the 6502 essentially not having a microcode level, this
> optimisation is exposed to the programmer.

The PLA is essentially equivalent to microcode.  The difference is
that it is addressed by the instruction register and a few state bits,
rather than a micro-PC.

Eric