Re: 65C816 adapter for 6502 computers (aka Apple II)

["M. Pender" <mpender@hotmail.com>]

On 3/20/04 2:50 AM, in article 20040320025042.20899.00000067@mb-m27.aol.com,
"Michael J. Mahon" <mjmahon@aol.com> wrote:

>> M. Pender wrote:
>> 
>> Note also that the timing of the 6502 is slightly different than the
>> 65c02/65c802/65816.  Thus, the 65c02 is not a drop-in replacement for the
>> 6502 on the Apple II or II+ -- IIRC it has something to do with the RDY
>> line.
> 
> Very interesting.  I've recently encountered my first card that relies
> on the RDY line for synchronization, so I'm quite curious about the
> details on this (now diving into manuals...).

I replaced the 65c02 with a 65c802 in my Laser 128ex back around 1990.  It
allowed me to use the broader instruction set of the 65816, but (IIRC) the
difference in logic timing was incompatible with the Laser's Universal Disk
Controller.  Faced with the choice of either gaining a few instructions or
losing the use of 3.5" disks, I opted for keeping 3.5" disk capability.

I remember running across my old 65802 processor in a box a few months
ago--I didn't realize they are now hard to get.

- Mike