RE: CommodoreWorld

From: Baltissen, GJPAA (Ruud) (
Date: 2004-07-03 16:25:58

Hallo allemaal,

Per wrote:
> The 27MHz number is misleading.  The Joystick will run at 
> 1MHz (adjusted for PAL or NTSC depending on where sold).

But still I wonder if it could emulate a C64 at 2 MHz, 3 MHz or whatever
clockspeed. In contrary to emulators, the VIC and SID are hardware. So if it
takes this ASIC, let's say, 9 cycles to execute one 6502 cycle, we still
have a C64 that can run at 3 MHz. Having extra registers to support the
extra features, I can imagine some bits reserved for 'overclocking'.

Per, you have a C-1, does it have a register for this?

> Actually no - the VIC article by Christian Bauer and the .....
> .... 
> Yes, and I believe the opcode mappings done by Marko and .....

Absolutely correct. But considering myself as a "hardware guy", I focussed
on the hardware itself. AFAIK mostly all the VHDL code for this ASIC is
developed by this person. 
Looking at my own hardware projects, I dare to say that some of them are
100% own developments. But looking at the above remark I must agree that
these developments are suported by the info given by other people.
So the next time I'll edit my site, I'll add a text, on the mainpage, giving
credit to all people and sites where I got my info from, OK? :)

gpz wrote:
> the 65816 doesnt have the illegal opcodes, so nothing of the 
> above that uses them will work.

That is so obvious that it even didn't come to my mind to mention it. Next
question: do you, or others, know of programs using these illegal opcodes?
I'm thinking of regular programs or games, not of demos.

> When the C-1 is emulating a 64, the actual CPU in use is a
> soft-NMOS6510 running in the 1K100 FPGA.  So, all illegals
> would be supported.

Interesting news! This most probably means that this C64-DTV supports
illegal opcodes as well. 
Gideon Zweijtzer, who is developing the 32-bits 6502, the 65GZ032, started
with coding a 6502 in VHDL first. He focussed only on the legal
instructions. Then he found out that his VHDL-6502 cooud execute almost all
known illegal opcodes as well. This supported the idea that all known
illegal codes are just a by-product of the legal ones. But we don't know how
the original engineers exactly implemented the instructions, so wanting to
have all illegal codes simply means extra work for us mortals.

I accidently deleted an email where Per expressed that his remarks were not
personally meant. Per, I understood that :)

Anyway, this whole discussion made me realise that it must be a tough job to
be a politician: you must watch every word you say! Look at the things I
said and how some of them were interpreted in a way I hadn't mean it at all!

I also want to end the discussion (if possible at all) by saying: I await
things to come. If things turn out wrong after all, it won't stop me doing
what I'm doing now: having fun with my Commodores. And I don't mind sharing
this fun, legal or illegal :)

   / __|__
  / /  |_/     Groetjes, Ruud
  \ \__|_\
   \___|       URL:



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