[Coco] Proprietary, nonstandard memory expansion for the CoCo

[Bruce W. Calkins]

I have the 256k J&R Banker on one of my CoCo 1s.  What he describes is not 
addressed the same.  There are utilities to use the J&R Banker under OS-9 
level 1.  At this point the hack needed is not understood well enough to 
make NitrOS9 work with it, yet.

Bruce W.

----- Original Message ----- 
From: "Arthur Flexser"

>I have zero useful input to contribute on this, but just want to see
> if my CoCo trivia neurons have come up with the correct tidbit on
> this:
>
> Was the 256K CoCo 1/2 expansion you're describing called the "J&R
> Banker" or something like that?
>
> Art
>
> On Fri, Jun 8, 2012 at 3:31 PM, Juan Castro <jccyc1965 at gmail.com> wrote:
>> This is a hack my (long-defunct) company did back in the day and I would
>> eventually like to replicate it in a real CoCo someday.
>>
>> It's a 256 KB memory expansion for the CoCo... 1 or 2. Basically, you
>> select, with a poke to some $FFxx, which of up to eight 32 KB banks will
>> play the part of the "upper 32 KB" in a 64 KIB CoCo. (Which you then 
>> would
>> select over the ROM in the usual way.) They raised one pin - SELECT 
>> pin? -
>> of each of the "native" upper 32 KB memory chips out of the socket, wired
>> them to one of the outputs of a 74LS138 and 6 of the other 7 ones to the
>> extra 192 KB in the expansion*. It worked pretty well, and although it 
>> was
>> compatible with precisely nothing, it was used in our in-house-developed
>> business systems. Which did sell, believe it or not. Not really being an
>> electronics person, I can't tell you what other chips were there, but 
>> would
>> it be too difficult to concoct some schematic based on that description?
>>
>> Being a total newbie in OS-9, I wonder how easy it would be to make
>> NitrOS-9 use that memory.
>>
>> Thoughts?
>>
>> * Yeah, that could theoretically make it a 288 KB memory expansion.
>>
>> Juan