[Coco] ECB+CB image (was: (no subject))

[Paul Shoemaker]

Thanks Amardeep!  I was thinking along those lines; thank you for explaining it so clearly.  I did get the windowed EPROMs but I haven't gotten a UV eraser yet.  That is next on my list...
-Paul

      From: Amardeep S Chana <asc135 at gmail.com>
 To: coco at maltedmedia.com 
 Sent: Saturday, October 21, 2017 9:23 AM
 Subject: Re: [Coco] ECB+CB image (was: (no subject))
   
On Fri, Oct 20, 2017 at 6:20 PM, <coco-request at maltedmedia.com> wrote:

> Date: Fri, 20 Oct 2017 19:05:23 +0000 (UTC)
> From: Paul Shoemaker <paulfe3 at swbell.net>
> To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
> Subject: [Coco] (no subject)
> Message-ID: <870631748.798990.1508526323014 at mail.yahoo.com>
> Content-Type: text/plain; charset=UTF-8
>
> Hi everyone,
>
> I started this thread on Facebook before, but I think it will be better to
> finish it here.
>
> I recently acquired a 26-3134A Korean 16K Color BASIC CoCo 2 with a
> #20261044 circuit board that I'd like to upgrade.  I've already upgraded
> the memory to 64K with some spare RAM chips I had (and I soldered the
> jumper at J6).  I'd next like to add extended color basic. I've purchased a
> programmer from eBay and have some 27128 eproms on the way as well.  This
> is the model of CoCo 2 which introduced a single 28-pin ROM socket.  I
> understand I need to replace the existing 24 pin ROM in that socket with a
> programmed 27128 EPROM, and also solder a few jumpers (J1 through J5).
>
>
> My question is about burning the ROM bin file onto the EPROM.  Since this
> single EPROM will contain both Color Basic 1.3 (8K) and ECB 1.1 (another
> 8K), my reasonable deductive skills tell me the bin file should be 16K in
> length.  There are several ROM bin files available in the archive.  Most
> are the individual 8K ones...  color basic, ECB and disk basic all
> separate.  Should I grab the ECB1.1 and CB1.3 individual 8K bin files and
> just concatenate them together?  Or is there a 16K combined ROM bin file
> out there already I should use instead?
>
> If by chance someone can point me to a step by step guide, that would also
> be outstanding.  I bought several EPROMs fully expecting to mess up on a
> couple before getting this figured out, but it also nice to do things right
> the first time with some help from one's friends.
>
> Thanks in advance!
>
> -Paul
>
>
Hi Paul,

In the CoCo memory address space, the Color BASIC ROM starts at $A000 while
the Extended Color BASIC ROM starts at $8000.  So to avoid crazy mapping
acrobatics, the simplest approach to combine them into a single ROM part
would be putting ECB at address $0000 and CB at $2000 of the EPROM.  This
could be accomplished by appending a binary CB image at the end of an ECB
image, then programming the combined 16K image into a 27(C)128 EPROM.  The
computer maps the EPROM start address at $8000 for that combination which
puts the images where they belong.

Creating such a combined image in Linux is very simple with a 'cat' command
or two.  In Windows you'd have to write some code or use the EPROM
programmer tool's facilities.  If you are not sure, I'd be happy to build
the image file and send it to you.

Incidentally, if you bought windowed erasable EPROMS, you can afford to
make some errors as you can just erase them and start anew.  Did you get a
UV eraser?  They're pretty cheap.

Best regards,
Amardeep

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