[Coco] Coco 1 question

[Mike Pepe]

Some pictures for reference included inline below:
 
> 
> 
> The CoCo 1 was for the most part known by the board revision letter.
> There
> are a few "C" boards in the wild with the "D" board being the first in
> major
> production.  "D" and earlier are more difficult to upgrade to 64k use
> what
> with trace cuts and adding jumpers.  All that considered, I keep any
> unmodified "D" boards as is for the historical value.
> 

Unmodified 4K D board:
http://www.doki-doki.net/~lamune/computers/coco/26-3001/P2233751-r.html


> 
> 
> The "E" boards only need a couple jumpers added to make user of a spare
> gate
> on the 74LS02 for the upgrade to 64k.  They are more common than the
> earlier
> boards.
> 

E-board 64k upgrade:
http://www.doki-doki.net/~lamune/computers/coco/26-3004/P2233817-r.html


> 
> 
> The last variant of CoCo 1 was the "F" or 285 boards. It did not have a
> letter after the board number but the board number ended in 285.  It
> supported 64k with built in jumpers.
> 

285/ET  board 32k upgrade:
http://www.doki-doki.net/~lamune/computers/coco/26-3002a/P2233781-r.html


 
> 
> As to the 26-3004A designation?  That would most likely refer to the
> Extended Basic ROM in a later model CoCo 1.  Without any other data I
> would
> guess it is the "F" or 285 board with Extended Color Basic.  Powering
> it up,
> if it does not blow a capacitor or two will show on the boot screen the
> Basic ROM version and level.  A PRINT MEM command will give the
> available
> RAM.  You won't know unless you open the case, look and decipher the
> RAM
> markings or enter PRINT MEM. As Robert stated; "with 32K RAM you will
> get
> 22824."  However I believe that would be for a system that has a Disk
> controller installed.  Non disk systems should show around 12584 for a
> 16k
> system, or 28968 for a 32k system using Extended Color Basic.  Color
> Basic
> only systems will show more available RAM and Disk Extended Color Basic
> used
> up another 6k.
> 
> 
> 
> Also be aware that a few of the early "F" / 285 board units had a
> timing
> issue and would crash about the time they warmed up.  There is a fix,
> but to
> the best of my knowledge it is out of stock.  Someone else may have
> some
> data on that.  I have one that I never did get fixed.  I keep it for
> spare
> parts for my other "F" /285 board CoCo 1.
> 
> 
> 
> Bruce W.
> 
> 
> 
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