[Coco] EPROM mods

[Arthur Flexser]

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
>
>