Date   : Fri, 11 Sep 1998 09:16:48 +0100 (BST)
From   : Carlo CONCARI <concaric@...>
Subject: 65C02 vs. 65C12 and Acorn ROMS

David Gorst wrote:

> Good luck with the emulator. Maybe I'll actually get to see the 128K
> version of Stryker's Run at last!

Thank you; I'm looking forward for it too! :->

> What's are the main differences between the 65C02 and 65C12 BTW?

First of all, I'm sorry for the long time it took to me to reply, but
I only have access to the Net at University and I live 30 km away from
it, so I can't be here everyday (well, not until lessons start
again... :)
The only big difference I'm aware of is that the 65C02 has four
instructions that are not implemented on the 65C12: BBR, BBS, RMB, SMB.
The 65C12 treats these four instructions as NOPs.
By doing some experimentation on my machine, I have found that they
increment the Program Counter by one and elapse only one clock tick.
BTW, I have found out the number of bytes and clock ticks consumed by
all of the unallocated opcodes of the 65C12, which are all treated as
NOPs; if someone is interested, just let me know and I'll post them.

Just another thing: is the ROM matter still unsolved? I've read the
archives of this mailing list and I've found some discussion two years
ago about the perverse behaviour of Acorn still wanting to hold their
rights on the ROMs. Even a guy from Acorn was subscribed to this list,
whose name was William Turner, who was supposed to be an intermediate
between emulator writers and Acorn bosses, but I haven't been able to
find anything on the archives about what he did.
Are you still here William? What are the current willings of Acorn's
high-located people? I think that by distributing the ROMs Acorn would
make more people able to use emulators, thus selling again some copies
of their games! (Well, I've never seen the BBC version of Elite, and
I'd eventually pay for it).

Ciao to everybody,
Carlo.