[Coco] Coco 1 question

[Bruce W. Calkins]

Jeremy Michea wrote:
Hi.

I picked up a Coco 1 and with manuals and 6 rompaks for $10 at a charity 
garage sale today and I looked at the model number on the back - 26-3004A. I 
can't find much info on this particular model. How much memory would this 
unit have and what's the difference between it and the 26-3004?

Thanks

=========================================
Jeremy,



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.



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.



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.



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.