Date   : Mon, 21 Sep 1998 20:08:18 +0100
From   : Stuart William McConnachie <stuart@...>
Subject: Re: 65C02 vs. 65C12 and Acorn ROMS

In message <Pine.SUN.3.95.980911091454.11562A-100000@...>, Carlo
CONCARI <concaric@...> writes
>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.
Could you tell me what their op-codes are and what they do!

>The 65C12 treats these four instructions as NOPs.
As it does all other illegal op-codes.

>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 a little curious.  I could measure them myself, but if you've
already done the work it would be useful to see.  Cheers.
Do you also know the cycle counts for the legal instructions.  I belive
these are different than for the original 6502.  BTW is that correctly
called a 6502A, and if so why have I never heard of a 6502B (Or is that
a stupid question?)

>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! 
But aren't these all owned by Superior?

Maybe we'll see some progress in this area now that I hear Acorn have
haulted development of any further new machines (Shame :-(((().  Since
they currently only licence use of the ROMs on Acorn machines this
policy now seems pointless (I guess the whole idea was to encorage
people to stay with the Acorn platforms?).

>(Well, I've never seen the BBC version of Elite, and
>I'd eventually pay for it).
Available on the web if you know where to look:
http://people.netcom.co.uk/i.bell/elite/Default.html

Works very well with my emulator:
http://www.bburne.demon.co.uk/bbc.html

Welcome back all!
-- 
Stuart McConnachie (stuart@...              )
43 The Hollows, Long Eaton, Nottingham, NG10 2ES, UK
Mobile: 0966 224307