[Coco] 2764 EPROM

[Gene Heskett]

On Saturday 08 September 2007, Bruce W. Calkins wrote:
>>> What Rodger is referring to is the later packs that had a
>>> small blob of black plastic in the middle of the small board.
>>>  Not a whole chip in sight.
>>>
>>> Bruce W.
>>
>> From: "Paul Fitch" <pfitchjr at bellsouth.net>
>> Well, it's the early pacs I'd think would be up for recycling.  Some of
>> those first rom pacs were were pretty lame.
>>
>> Still, what he really needs it what he originally asked for.  A stack of
>> blank PCBs suitable for plugging into the expansion port of the Coco.
>> Radio
>> shack used to make something like that, but I doubt there are any left.

I'd almost bet a run of 100 of those would slowly evaporate.  Humm, a good 
project for my mill maybe?  If someone can do the drafting, and send me 
something I can make into RS-274C g-code with a gerber translator or similar, 
I'd be willing to go get some plated board and try. They should be Single 
Sided after the edge connector, and no plated thru holes though.  I have 
carbide bits going down to 1/16" and could find smaller I believe.  I'm 
hoping the new Z axis drive I'm building will allow that precise a control 
over depth.  No nasty chemicals involved when done this way.

>The very early ROM packs used 4K ROMs, Sometimes two of them.  Later
>versions used a single 8k ROM.  I combined two of them into one by
>piggybacking the chips with a switch to select between them.  By the time
>things evolved to the 16K ROMs they were apparently SMDs covered with a blob
>of black plastic looking stuff.  There may be a few other variations,
>especially among third party sources.  However I have not seen anything that
>had all the address lines needed for a 16K EPROM that could take a socket,
>or a conventional DIP chip.
>
>
>
>There were a few boards from Radio Shack and others that plugged into the
>CoCo port.  Most only had solder tabs on the port end.  I built an EPROM
>Burner on one.
>
I made one too, many years ago, that interfaced with the SS-50 bus of a z-80 
board, cost about $25 at the time & a third of that was the ZIF socket.

>There are several on this list that would be interested in prototyping
>boards, if it did not break our banks.  I am thinking along the line of ones
>with a socket for a 8K to 32K EPROM.  Perhaps with bank select switches and
>space to work up other projects.
>
>Bruce W.

-- 
Cheers, Gene
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