[Coco] Coco 1 question

[Jeremy Michea]

You may be right. I can't get this unit to turn on at all. It seems 
completely dead. Oh well, I'll keep it for parts. I'm not a "techy" so I 
can't fix it.
Thanks for your help everyone.
Jeremy

----- Original Message ----- 
From: "Bruce W. Calkins" <brucewcalkins at charter.net>
To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
Sent: Sunday, November 22, 2009 7:22 AM
Subject: Re: [Coco] Coco 1 question



> 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.

>

>

>

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