which instructions are really necessary (maybe all of them?) and why it would be inconvenient if you didn't have a particular instruction The ones added in the

which instructions are really necessary (maybe all of them?) and why it would be inconvenient if you didn't have a particular instruction The ones added in the 65C02 offer some insight there, a very brief overview from the Wikipedia page: https://en.wikipedia.org/wiki/WDC_65C02#New_and_modified_instructions https://en.wikipedia.org/wiki/WDC_65C02#New_and_modified_ins... Somewhat related and mentioned in one of the comments downthread, you can view Woz's SWEET16 as a 'the 16 bit CPU a 6502 system designer and programmer wished they had' take.