[Coco] possible CoCo ROMPak mod tweak? : 32K

[Chad H]

I hadn't thought of that use for it.  That's right, some CoCo 3 users put 32k EPROMS inside the machine itself huh.. And this might be a easier less intrusive and less permanent option I guess. Aren't the required internal chips also harder to come by than the 27256 equivalent?  How many ROMS, especially popular ones, are there that actually require the 32k?

I was just about to order another batch of the PCB's.  I'll look at performing the design modification first.

Sent from my Asus Transformer Infinity

-------- Original Message --------
From: Kip Koon <computerdoc at sc.rr.com>
Sent: Tuesday, November 11, 2014 03:49 PM
To: 'CoCoList for Color Computer Enthusiasts' <coco at maltedmedia.com>
Subject: Re: [Coco] possible CoCo ROMPak mod tweak? : 32K

Hi Chad!
Sounds like an interesting way to circumvent the internal 32KB eprom in the
Coco 3!  I like the idea!

Kip Koon
computerdoc at sc.rr.com
http://www.cocopedia.com/wiki/index.php/Kip_Koon


-----Original Message-----
From: Coco [mailto:coco-bounces at maltedmedia.com] On Behalf Of Chad H
Sent: Monday, November 10, 2014 11:50 AM
To: 'CoCoList for Color Computer Enthusiasts'
Subject: [Coco] possible CoCo ROMPak mod tweak? : 32K

This is in reference to the modified versions of Mark Blair's EPROMPak
boards I've been making and the usefulness of the ability to 'bank' in 32k
segments.  (http://www.nf6x.net/tag/cocoeprompak/)

His original board has 2 banking jumpers, together they select a 16k 'bank'
of the EPROM for loading, up to 4 banks available if using a 27512 (64k).
It does this by toggling the A14 & A15 address lines.   The A13 line was
permanent tied to the bus which permitted no manual setting for 8k sections.
I added a 3-way jumper for the A13 that allowed one to select one of both
the 8k pieces of the 16k section OR run in the original bus controlled 16k
mode.  This has worked wonderfully for 8k banking ability.  However, and
this doesn't effect me directly since I don't personnal own a CoCo 3, just a
CoCo 2, I've been asked about doing 32k banking.  I do seem to recall that
the CoCo 3 could address a full 32kb on EPROM, which must be one of the
reasons why a lot of the newer Radio Shack ROM games were CoCO 3 only.  Yes
I know there are other reasons too,  but my question is how beneficial is it
to EPROMpak users to have the ability to load 32k images?



It won't be that hard or time consuming for me to modify the board again to
allow this.  All I would have to do is change the A14 jumper to a 3-way just
like I already have on the A14 line.  Since the A14 jumper normally selects
16k sections, tieing it to bus control should allow the CPU to 'float' a
full 32k between 2 16 k sections.  This 32k section would be selected by the
remaining A15 jumper and would provide 2 x 32k banks on a 27512 chip or
allow for  a full 32K single image to be accessible on a 27128 chip.



I suppose I could go ahead and make the modification anyways as it doesn't
really add any cost to the assembled board and it wouldn't require much time
at all for me to modify the design.  I just hate wasting time doing things
that seem 'cool' but otherwise end up being useless in practice.  Soo.. any
thoughts from the CoCo EPROMpak users?


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