6502 vs. 6800 (was Re: kits, definitions, prices...)

From: Eric Smith <eric_at_brouhaha.com>
Date: Wed Oct 7 20:32:42 1998

I wrote:
>> Was going to? They did. It's called the 6501. I've got one. I just
>> need to get a 6800 system to plug it into :-)

Cameron Kaiser wrote:
> But Motorola nixed it for copyright/patent reasons. MOS agreed to change
> the design, made the 6502, and the rest is history.

Actually they had already designed the 6502, for use in new designs where
pin compatability with the 6800 was less important. The 6502 only needed
a single-phase clock input rather than the two-phase non-overlapping clock
required by the 6800, which made it somewhat easier to design with.

Apparently Motorola didn't consider the 6502 to be as much as a threat,
since it wasn't a drop-in replacement.

>> Trivia question of the day:
> ROR, I believe.

We have a winner.

> It appears on models after 1976, IIRC.

According to my docs, Sept. 1975.

I've always wondered whether the ROR was originally planned but just didn't
work on the first silicon, or whether it was added to the design later. I
haven't tried running ROR on my 6501 or early 6502s to see what happens.

Eric
Received on Wed Oct 07 1998 - 20:32:42 BST