How many transistors in the 6502 processor?

From: Cameron Kaiser <spectre_at_stockholm.ptloma.edu>
Date: Fri May 4 17:10:44 2001

> Many looked at the zero-page and the 8 bit stack pointer as shortcomings.
> It was the X and Y index registers both 8 bit, that made the chip interesting.
> The X/Y pair made memory-madpped video graphics easier to implement.

Zero page is not a shortcoming, but instead one of the 6502's better features.
It basically works out to giving you optimized access to a segment of RAM
-- almost like 256 extra registers. Other chips have used a similar scheme,
including the TMS 9900 and friends (like the 9995, which even keeps this RAM
onboard for really high speed access).

The stack is truly a bummer, but there's software ways around that.

FWIW, the later 65CE02 deals with both these issues. You can "move" zero page
anywhere in memory you want on the fly (so that you can pick a memory page
and optimize access to it), and the stack pointer is now 16-bit. The 65CE02's
most well-known usage was in its guise as the CSG 4510 in the mythical
Commodore 65 (see

        http://www.retrobits.com/ckb/secret/65.html

).

-- 
----------------------------- personal page: http://www.armory.com/~spectre/ --
 Cameron Kaiser, Point Loma Nazarene University * ckaiser_at_stockholm.ptloma.edu
-- The world only beats a path to your door when you're in the bathroom. ------
Received on Fri May 04 2001 - 17:10:44 BST

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