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What am I forgetting?

amauget

Experienced Member
Joined
Mar 9, 2011
Messages
84
I have to check but I don't think a 65C02 won't work in an Apple II+.
The only problem I see are the false opcodes used in disk protection scheme that would be interpreted differently, leading to a crash.
 

george

Experienced Member
Joined
Apr 1, 2011
Messages
407
I have to check but I don't think a 65C02 won't work in an Apple II+.
The only problem I see are the false opcodes used in disk protection scheme that would be interpreted differently, leading to a crash.
That's because you think as a good programmer... But between NMOS and CMOS versions there are several electrical differences I guess...And the way a ][+ is buffering NMOS CPU is a problem...
 

KC9UDX

Space Commander
Joined
Jan 27, 2014
Messages
7,468
Location
Lutenblag
Thank you guys, there's a lot of good information here. I didn't realise the timing was that tight on the ][. I guess Woz did the wrong thing, or just the right thing, by making it just barely work, yet work very reliably at the same time.

The //c and ][+ may be significantly different. For some reason I always disliked the //c, so I don't own one. I do have a ][e which I can play around with for comparison. Sadly, that ][e did have a R65C02 in it, (Rockwell), but I sold it to someone who wanted an Enhanced //e, because I wanted to return that machine to it's original non-Enhanced state. Else, I'd have more things to try.

I may have an additional R65C02 around somewhere, I'll have to look.
 

KC9UDX

Space Commander
Joined
Jan 27, 2014
Messages
7,468
Location
Lutenblag
I put in a Rockwell 338-6503 (What were they thinking with that nomenclature??) and it works!

So do I now have an "][+ Enhanced", a "][,", "][++", a "][*", a "//e-", or what? :eek:
 

barrym95838

New Member
Joined
Oct 12, 2014
Messages
7
Location
California
I had some fun playing with a 65c802 in my ][+ back in the early 90's. As long as your software doesn't depend on the behavior of undefined NMOS opcodes, the 'c802 is a better hardware match to the NMOS unit cycle-for-cycle than the 'c02 is. I could run Integer BASIC, Applesoft and DOS 3.3 without issue or modification, and I was working on patching the mini-assembler and monitor 'L' command for all the new instructions before I wound up abandoning it for something else that seemed more interesting at the time.

It's a shame that WDC stopped making the 'c802 ... it was a full 'c816 inside, but could only output 16-bit addresses, which wound up being perfect for plug-n-go retrofit experiments like mine.

Mike
 
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