[Coco] EPROM mods

[Bob Devries]

Thanks, Art. Just what I was looking for.

Regards, Bob Devries
Dalby, QLD, Australia

----- Original Message ----- 
From: "Arthur Flexser" <flexser at fiu.edu>
To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
Sent: Friday, June 14, 2013 6:15 PM
Subject: Re: [Coco] EPROM mods


> Bob, here's an old bit of correspondence that I dug up that should
> have the information you need.
>
> Art
>
>
>>
>>Well, the FD501 has a 24-pin ROM socket, so you will need to jumper 
>>things.
>>
>>Here's what you need to do to get it to take a 28-pin EPROM. First, on the
>>EPROM, bend pins 20, 23, and 26 outward slightly so that they don't plug
>>into the socket.  The EPROM will plug into the socket with its pins 1, 2,
>>27, and 28 hanging off the end of the socket.
>>
>>An E stands for a pin of the EPROM, S for a pin of the socket.
>>
>>Connect:
>>  1E to 27E, 28E, 24S (alongside bent-out 26E)
>>
>>  2E to 21S (alongside bent-out 23E)
>>
>>  18S (alongside bent-out 20E) to bent-out 23E
>>
>>  22E to bent-out 20E
>>
>>  bent-out 26E to pin 37 of the edge connector
>>
>>
>>
>>That last connection, involving running a wire to the edge connector, is
>>only necessary if you anticipate using a 16K EPROM in the controller (Disk
>>BASIC and ADOS take up only 8K; you'd probably only need this if you later
>>acquire a CoCo 3 and want to use Extended ADOS-3, which requires a 16K
>>27128 EPROM.)
>
>
>
> On Fri, Jun 14, 2013 at 3:10 AM, Bob Devries <devries.bob at gmail.com> 
> wrote:
>> Can someone refresh my memory about how to install a 28-pin 2764 EPROM to 
>> replace the 24-PIN ROM in a Tandy disk controller?
>> I seem to remember a little PCB that does the conversion, but I should be 
>> able to do it without that; I just can't remember the details.
>>
>> Regards, Bob Devries
>> Dalby, QLD, Australia
>>
>>
>
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