Coco Nutz! Vol 3 Issue 2, May 2007.pdf - TRS-80 Color Computer ...

CoCoNuts! May 2007 Volume 3 Issue 2
T H E L I F E A N D T I M E S O F T H E C O L O R C O M P U T E R
drive (5 1/4" and 3.5" respectively),
there was also a port that allowed
plugging up an external drive. More on
this later.
Probably the most curious observation
was that the prototype did not even
have a GIME chip. The GIME was a
custom IC created to handle things
like graphics and memory. In the early
prototype stages, before such an
expensive chip could be made,
designers created the functionality of
the GIME using programmable PAL
chips and other support hardware. It is
unknown how much GIME support is
on the prototype, but since Microware
used it to create the Extended Color
BASIC enhancements (which included
the new graphics modes), and since
the prototype had 512K, is believed to
have implemented the graphics and
memory controller that the GIME later
would handle.
There could be other secrets in this
prototype. Early developers, under
Non Disclosure Agreements with
Tandy, received pre-production CoCo
3s with pre-production GIME chips.
There were two known revisions to the
production GIME (86 and 87 revision),
and the early development units are
believed to have been just earlier (and
buggier) versions of what was released.
But, documents given to
Microware during this project indicated
that one of the specifications for the
CoCo 3 was a 256-color mode. Steve
Bjork has stated that this mode never
existed in any manufactured CoCo 3s,
and notes that the graphics hardware
itself did not have enough bits available
to represent a 256-color map.
However, this early prototype may
have had the basis for such a mode
before it was deemed either too costly
or, perhaps, too likely to compete with
the Tandy 1000 graphics. The mystery
of the specified 256-color mode
may finally be unlocked in these
early designs.
In a side note, the whole suspicion of
a 256-color mode started when a
former Tandy Color Computer product
manager made reference to it years
later. "Has anyone found the 256 color
mode?" he asked. No one had, but
noted Color Computer programmers
John Kowalski
("SockMaster") and Australia's Nick
Marentes were able to find abnormalities
in the CoCo 3 schematics published
by Radio Shack in the Color
Computer 3 Technical Service Manual.
As Steve Bjork has mentioned, there
were not enough address lines for
doing an 8-bit color, but the schematics
showed some evidence of alterations
in that area. There where two
extra lines being routed away from the
normal path. Perhaps there were plans
to achieve the 256-color mode by some
way that would allow accessing those
extra lines? Nick was able to track
down the original designer of the GIME,
but he had no recollection of any such
mode. It seems likely that this mode, if it
ever existed, may not have even made
it to the GIME stages.
So the prototype, while not quite a
"blue sky" machine with enhanced
sound and true RS-232 serial hardware,
did certainly represent a somewhat
nicer machine than what was
actually released. Imagine a CoCo 3
with 512K standard, normal DB9
monitor port on the back, and a place
to plug the disk drive ribbon cable in
and still have the cartridge port
available. This would have removed
need for the MultiPak for the large
number of CoCoists who used floppy
and RS-232, or perhaps floppy and
the Speech/Sound Pak.
When the prototypes are fully inspected
and, hopefully, reverse
engineered, there may be more
mysteries discovered. Though the
prototypes were supposedly working
when they were packed away 20
years ago, until someone qualified has
time to inspect them, no attempts are
going to be made to power them up.
The conclusion in the next issue of
CoCoNuts!
Allen's CoCoFest Map
Drop by and place your mark on the map. This
will not only give an idea on who all is going (or
may be going), but it can be used to help coordinate
ride sharing (if that helps some folks attend
who might not otherwise get to attend).
http://www.frappr.com/cocofest2008
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