[Coco] Cryptic BASIC program

[Salvador Garcia]

Thanks all for your feedback and explanation of the code.
 
Although I understood all that was explained, I am not sure exactly what effect this small program has when I run it. I remember the Radio Shack guy telling me that I had to run it in order for the CoCo I to recognize all 64K; however, given the 1600/16000 discrepancy, I am not sure what the code as given actually does. I need to get more stuff done, but if I have time I will unpack the CoCo I and try out both versions of the code to see if I can detect any difference.

Again, thanks, I appreciate your time in effort in helping me out.

Salvador

 
 
-----Original Message-----
From: Arthur Flexser <flexser at fiu.edu>
To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
Sent: Sat, Sep 26, 2015 10:56 pm
Subject: Re: [Coco] Cryptic BASIC program


On Fri, Sep 25, 2015 at 11:18 PM, Darren A <mechacoco at gmail.com> wrote:

>
> It
is not a good substitute for a real RAM test program. It merely checks
> the
jumper setting which Basic uses at initialization time to decide how to
>
configure the SAM chip.  I'm not sure if the CoCo will even boot correctly
>
when the SAM is configured for the wrong type of RAM chip.
>

I recall you could
fool a 32/64K CoCo 1 into setting the SAM for 4K by
pressing the reset button
with shift and break held down, so
apparently CoCo Basic will tolerate a wrongly
set SAM configuration in at
least some cases.

(This was the basis of the
shift-break-reset method of breaking out of a
copy-protected program, allowing
certain special methods of removing the
copy protection to be employed.  Not
usable with Color Basic 1.2 (?) and
above due to the elimination of checking for
the 4K possibility in later
versions of Basic's warm start routine.  After
shift-break-reset, most
commands give an out-of memory error in the 4K
configuration, but CLOADM
and EXEC work, so you can regain control of the
machine and switch back to
64K SAM mode.)

Art

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