Re: Accelerating the CPU!

[jcompton@typhoon.xnet.com (Jason Compton)]

Rubywand (rubywand@swbell.net) wrote:
: Jason Compton writes ...
: > 
: > I'll take your inflammatory remarks in good humor. :)
: >
: 
:      The C-64 really is a simple machine. This simplicity makes it easier to 
: produce an upgrade which can be selectively bypassed when running old programs.

While I realize that the original post was about the IIGS and not the
II+/e/c, don't they far outstrip the 64 in terms of architectural
simplicity?  The 64 does after all have a few custom chips and not much of
an expansion bus.

:      Most C-64 wares are games and most of these were designed to run fine at 
: normal speed. The main C-64 user-convenience bottleneck has always been disk 
: access. Aside from applications like GEOS, there would seem to be little gain in 
: running old C-64 wares at 20MHz or 200MHz.

Most C-64 GAMES were designed to run fine at normal speed, that much is
true.  However, the number of applications that benefit (GEOS and other)
is significant.  And then there are games which were SOMEHOW released for
the 1 Mhz machine (like the filled polygon game Total Eclipse) which
suddenly become playable at 20.

: > The 20mhz '816 board actually does a surprisingly GOOD job of running old
: > software ....
: 
:      What are the board's specs? What is its price?

The expansion box is $200.  That gets you a unit which plugs into the
cartridge port (with a passthrough), the aforementioned '816 running at
20mhz, enough RAM to shadow the 64's RAM so it all works, and JiffyDOS
built in.  For another $100 or so, one of these days you'll be able to buy
a RAM card add-on.

:      How do you deal with arcade games? For example, does each ware have to be 
: deprotected and modified?

No.  There are three things which could cause an arcade game to fail.

#1.  Incompatibility with JiffyDOS.  The answer to that one is pretty
simple, just switch JiffyDOS off.  (There's a switch on the top of the
unit which lets you enable and disable JiffyDOS at will, while the machine
is running.)

#2.  Game can't access the disk properly at 20 Mhz.  The answer can be
simple, and is theoretically rock solid, but isn't so in practice.  If the
game is using custom loading code, that code will usually choke at 20 Mhz.
There's a switch on the unit which lets you toggle between 1 Mhz and 20Mhz
at will while the machine is running, BUT, a small percentage of the time
the switch will kill the program.  The success rate of this technique
depends on the game--if it's just the initial load that's a problem, no
big deal, you just throw it in 20mhz mode when it's done loading.  For
some games which load while you play, it depends.  Clever games, like
Neuromancer and Echelon, will prompt you to fix the drive if the load
routine fails.  Others, like Flight Simulator II, just die (and there's no
good way to figure out when FS II is going to hit the drive.  CMD tried to
figure that one out for a long time because apparently it looks great at
20 Mhz.)

#3.  Game uses undocumented opcodes and fails.  Short of modifying the
code as you suggest above, there's nothing to be done here.

(A very small category of games could fall into #4, where they will refuse
to run if they detect that ANYTHING is in the cartridge port)

: > compatibility is of primary concern since there's
: > really no SuperCPU-only software right now.
: >
: 
:      Too bad. What projects are 'in the works'?

I've heard of an attempted raytracer, a few people are planning to
develop games that take advantage of the SuperCPU...

:  What sort of Display (resolution x number of colors) is available to
: 1990's : C-64 users? Has Sound been improved? Has C-64 DOS been
: improved? 

Someone more technically oriented than I could better answer the display
question.  There are all sorts of wacky display modes out there which take
advantage of glitches of the VIC-II chip's design, from expanding the
color palette to interlacing the display.  I've heard of modes which allow
up to 56 colors on screen, by tricking the VIC-II chip into internally
laying half-pixels on top of each other.

Dual-SID (6 voices) sound has been around since the late 80s.

The aforementioned JiffyDOS is as good as it gets for 64 DOS.  JiffyDOS
speeds up virtually all disk access by an appreciable amount, and is the
core of the CMD 3.5 inch floppies and their hard drives as well.

-- 
Jason Compton                                jcompton@xnet.com
Editor-in-Chief, Amiga Report Magazine       Anchor, Amiga Legacy
http://www.cucug.org/ar/                     http://www.xnet.com/~jcompton/
Move forward...                              ...was my friend's only cry