[Coco] (Probably stupid and newbie-ish) CoCo hardware question

[Aaron Banerjee]

I consulted my "spellbook" on the matter.

For each case, use 64K chips.

1.  For the older "grey" Color Computer I, check your motherboard.

     If the serial number ends in an "E", you have an "E" board.   
There are a bunch of capacitors to remove and a few jumpers to set.   
I've got a poorly hand-drawn diagram that I'll upload if anyone is  
interested.
     If the serial number ends in a "285", you have an "F" board.   
There are 8 capacitors to clip, three jumpers to set to "64K", and one  
to install.  Again, I have a poorly drawn diagram if you're interested.
     There is a way of upgrading the "D" board, but it is more  
involved.  Please hope you don't have one.

2.  For Coco 2, remove the keyboard.  There is a solder point to  
connect (W1).  It is almost too easy.  For models 26-3134 and 26-1636,  
there is a jumper wire that needs to be installed.



To actually use all 64K, try this program:

5  DATA 26,80
10 DATA 142,28,0
15 DATA 166,132
20 DATA 183,255,223
25 DATA 167,128
30 DATA 183,255,222
35 DATA 140,255,0
40 DATA 38,241
45 DATA 183,255,223
50 DATA 28,175
55 DATA 57
60 FOR X=3584 TO 3609
65 READ D
70 POKE X,D
75 NEXT X
80 EXEC 3584

If you get a ?SN ERROR in line 80, you don't have BASIC.  Try:

80 POKE 157, 14
85 POKE 158, 0
90 EXEC

instead.


After running this program, you should be able to POKE into any memory  
location.  Try something up in cartridge memory (e.g. poke 49152, 9)  
and see if you actually get a "9" when you PRINT PEEK(49152)

             - Aaron

#include <std.disclaimer>

Note:  I typed that program out of a notebook that is about 25 years  
old.  If it just goes "kerplunk", I might have not read one of the  
numbers right.  The DATA statements correspond to instruction/operand  
pairs (e.g. making it easier to figure out what the actually assembly  
program is, which I did some time ago, but seem to have lost it).


On Jun 25, 2012, at 2:54 PM, Bruce W. Calkins wrote:

> The original CoCo 1s were in one way or another capable of using all  
> 64k of the standard 64k chips.  Some of the earlier ones has a  
> switch (jumpers) for selecting the top half or bottom half as the  
> addressable portion addressed by basic as a nod toward "half-good"  
> 64k chips that never did gain any significant market share.  Using  
> the full 64k was a relatively simple matter of wiring in an unused  
> gate on a 74LS02.  By the last version of the CoCo 1 and all CoCo2s  
> the addressing for use of the full 64k was in place.
>
>
>
> Short answer; in all probability a 32k CoCo 1 or 2 is actually a 64k  
> CoCo. There is a program to test for 64k addressing out there  
> somewhere.
>
>
>
> Bruce W.
>
>
>
> =====================
>
>
>
> ----- Original Message -----
> From: "Juan Castro"
>
>> Let's say you have a CoCo 1 or 2 with 32 KB RAM.
>>
>> Is it possible to provide the standard additional 32 KB through a
>> cartridge? Or do I necessarily have to open it up and put the DRAMs  
>> inside?
>>
>> Juan
>
>
>
>
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