[Coco] No more dream ports (Was:Wolfenstein 3-D on a 4.77mhz 8088? So, 6809 port, anyone?)

[Steve Bjork]

Good Call Nick.  It's so nice to hear another programmer chiming in that 
knows limits of the CoCo and what modern computers have to offer under 
the hood.

Now it's time for my rant....  (But not directed at you Nick)

I see messages like this where someone wants to port a modern web 
browser or some game designed for a system with a 3-d graphics processor 
to a decades old coco.  Stuff that was only design now because we have 
the hardware to support it.

A bit mapped graphics screen of the CoCo is easy to understand and 
program for.  But it's bear to try any fast moving (scrolling) 
graphics.  The other systems (of the CoCo days) like NES, SNES, Genesis, 
Atari and C-64 have character bases screen maps that use less memory and 
built-in hardware to scroll or update the screen. All of these systems 
had hardware sound generators.  Some even had a second CPU just to run 
the sound system.

Now, the CoCo only has one CPU.  Yes, a good 8-Bit CPU.  But the Sega 
Genesis had 68000 (16-bit) for the main CPU with a Z-80 to run the sound 
system.  Add in hardware graphics system with DMA and Sprites and you 
can see why the CoCo was not up to doing these types of fast scrolling 
games.

The goal of a CoCo programmer should be to make a game that plays within 
the limits of the hardware.  There are a lot of good games that could 
done and not show off the limits of the CoCo.

Marty's Nightmare is one game type that works well in the limits of the 
CoCo 3's hardware.  It has smooth vertical scrolling used the hardware 
to change the address of the CoCo 3's screen memory. In other words, it 
took almost no work to scroll the screen since you did not need to move 
the whole game image around in memory. It would not be hard to create 
other fun playing games using this vertical scrolling technique.

Here is a link to a video of Marty's Nightmare: 
http://www.youtube.com/watch?v=0Cvun0UZDfE
(Skip about 1/2 in to see the game in action.)

This smooth vertical scrolling technique is not limited too just two 
screens high.  It would be very easy to do a continuous vertical 
scrolling shooting game like Xevious or 1942.

Yes, the CoCo was a fun little computer and the 6809 is still my 
favorite CPU to code for.  I'm sure you will agree with me that it's 
time to work what can be done (and fun), not something to just showoff 
how great your purchase was 30 years ago.

Steve

On 4/24/2013 1:40 AM, Nick Marentes wrote:
> I think a port of the Wolfenstein source code  is pointless.
>
> You can see how slow it runs on a 4.77Mhz PC so it will run even 
> slower on a 1.79Mhz 6809.
>
> I think the key here is "remake" rather than "port".
>
> If a Wolfenstein 3D is custom written for the CoCo using new 
> algorithyms tailored for the CoCo, then you may get closer to the 
> 4.77Mhz PC.
>
> Substitute Sock Master's "Gloom" engine will be faster than a direct 
> port of the existing Wolf3d code which was written for a faster than 
> 4.77Mhz processor.
>
> Even then, the texture mapping will be a big speed drain.
>
> My Gate Crasher utilized the "Gloom" engine concepts at a lower res 
> but it still pales to Wolf 3D.
>
> Writing it to suit the CoCo-X (if it ever appears) will not happen for 
> such a small user base.
>
> Nick
>