heuser.marcus@freenet.de wrote:
Can MOS 6502 be replaced with WDC65C02 Microprocessor? The WDC can fit with Atari 8bit family and Apple II family...Apple II -> yes Atari 8 bit -> no! (at least not as a simple replacement) The Ataris use a modified 6502 - called 6502B. It differs in only one feature from the normal 6502: It has a special interrupt line which the graphics processor ("ANTIC") uses to stop the 6502 and gain DMA access to the RAM. The 6502B is therefore not pin-compatible. You 'd have to build extra circuitry to add this interrupt line to a "standard" CPU like the 6502 or 65C02. And if you have to do that you may use a powerful CPU like the 65816. (Then a plethora of other problems will arise - like system timing. But that's another story .)
Mostly right. The early Atari 800 used 6502B and the later 800s through the XEs used a 6502C. Only the processor board for the early 6502B has the extra circuitry you need to use a 65C02.
I have a 65C02 in one of my 800s. In my experience it does nothing but a little power saving unless you write your own code in assembler. I seem to recall my code was ~5% shorter using the extended instruction set. I've got in debates with people about the value of 5% tighter code. I think the ~5% speed gain you get is not significant but freeing up 500 bytes in the OS ROMs would allow you to add some nice features.
There was also the 65808 that is supposed to work in early 800s. This is a 16 bit internal/65816 pin compatible with the 6502B. I tried for a year to find one of these in every surplus shop in Silly Con Valley w/o sucess.Maybe we could scrape together a million bucks and get WDC to make another run.<grin>
Just a general comment to the group. Most people don't want to learn a new language like Action! or assembler. People that don't solder don't want to learn at this stage of their lives. What people seem to really want is a new power supply that will let their Atari run like a gigaHz P4.