[Coco] Banking ROMS (was-6309 microprocessor project: 11-01-2003)

[Roger Taylor]

Steve Bjork,

I have admired your CoCo accomplishments since the beginning of my CoCo days.

Now, dern it... how did you create the "We Gotcha!" vocals in your Mega-Bug 
game?!  :)  I hacked that game when I was about 17 years old and discovered 
a sort of compressed format, where the values were delays between speaker 
clicks, I think.  Anyway, I've always wanted to know that.

changing the subject a tad..

I have created what I believe is the ultimate CoCo assembly programmer's 
dream.  I'm currently calling it Portal-9.  Windows is required.  Most 
EDTASM source code is supported.

Tonight I finally got to the point where I can build my Projector 
multiviewer system (a quite modular disk program), with *one click*.  Some 
35+ source components are wizzed through automatically, spitting out what 
is needed for the floppy disk image; everything is copied over to it in 
exactly the right format and type; it's mounted in M.E.S.S., and you are 
ready to type LOADM "P3" and go.  ROM Paks start up and run 
automatically.  Ofcourse, emulation features are optional at any time.

It's quite amazing.   I will probably be releasing a demo version sometime 
this coming week or earlier.

Cheers







At 12:38 PM 11/1/2003 -0800, you wrote:
>Good Day John,
>
>Trying to remember from a "A Long Time ago on a computer far far way...."
>(Back when I worked with Tandy on creating Games for the CoCos)
>
>  The Color Computer 1&2 had a simple ROM limit of 16k.  With the 
> introduction of the CoCo 3, the ROM limit was double to 32k by using the 
> option of disabling internal 16k BASIC ROM.  But that is the limit to the 
> standard ROM Pak.
>
>There are two reasons for the limit.  First is the size to the CPU's 
>addressing window to the ROM Pak. In the case of the COCO 1&2 the limit 
>was always 16K.  In the case of the COCO 3, the internal ROM could be 
>disabled to expand the CPU's addressing window to 32k.
>
>The second reason for the limit is ROM addressing did NOT use the same 
>addressing system as the RAM.  While RAM uses a bank control system (via 
>the GIME) to page in the memory, the ROM get's its addresses straight from 
>the CPU without any page bank.
>
>So how do you access more than 32k of ROM on a COCO 3? You must put the 
>ROM banking circuit on the cartridge. While this is not unheard of (common 
>on the Atari 2600), not so for the COCO because this would double if not 
>triple the cost of the COCO 3 Game Pak.  I don't recall any Game Paks 
>released with more than 32k because of the overriding cost issue.  (But I 
>could be wrong.)
>
>My Rampage game did use 32k ROM, but it was hard to fit in that small of a 
>package.
>
>I remember hearing a story about how useful Rampage.  The COCO guys back 
>at Tandy had display a CoCo 3 and Tandy 1000 side by side with both 
>running the game.  In walk the execs for the COCO and PC (Tandy 1000) 
>lines and start looking over the game running the two computers.  After a 
>few minutes, the PC guy said to all of the other execs  . . .
>
>"This is why we need to kill off the Color Computer, just look how much 
>better the PC version is over the Color Computer version!"
>
>One the COCO guys steps up and said "Sorry, But that's the Color Computer 
>you are pointing to."
>
>Not only did the PC exec have egg on his face, but the Color Computer line 
>was saved that day!
>
>Just a moment in Color Computer History.
>
>Steve (6809er) Bjork
>
>At 08:20 AM 11/1/2003 -0500, you wrote:
>>Could someone explain how the newer coco3 rom cartridges worked.  The 
>>ones that accessed
>>more then 32K ROM?  Where the ones that did use more then 32K using the 
>>same memory map
>>and switching methods?  How did these rom cartridges switch memory 
>>in&out?  What was
>>the most ROM, a cartridge ever used?
>>
>>Any help appreciated; thanks.
>>
>>John Collyer
>
>
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