Date   : Fri, 07 Mar 2008 18:46:01 +0100
From   : dw@... (David Warrington)
Subject: TUBE chip, accessing 'Parasite' side - 16Mhz 65C02S

This issue about instability of 65C02 as a chip swap in the beeb is 
interesting. I hadnt heard about this before.

I remember buying a "65C02" from Rapid Electronics (with the red 
catalogue... I can still remember even though 20 yrs ago), and sticking it 
into the beeb, and taking out the BASIC2 ROM, and replacing it with a BASIC4 
EPROM rip from a Master at school. And it all worked flawlessly. 
Standalone, with disk drive, with teletex adapter, with EPROM programmer, 
with AMX mouse, etc.  I guess I was lucky!!

I later upgraded to the solidisk 4MEG board that ran the been at 4MHz with 
65C02. That was also rock solid.

I had no software conflicts. I understand the issue of illegal opcodes, but 
perhaps the software I was using stuck to documented opcode. Interesting to 
hear the Zalaga was DESIGNED for illegal opcodes. I wonder why? Perhaps it 
was used in the anti-copy code to make it very difficult for people to 
disassemble and work-around.

When I get a chance to get attack the attic, I'll take a look at the 65c02 
stuff and report back.  As I said earlier, running BASIC4 was a major 
improvement on BASIC2. Faster. And more accurate math. Plus a sense of "I've 
upgraded the machine and its up to date".  Pretty important to a teenager in 
1984/5. LOL.

David