[Coco] Seeking: ECB ROM chip

[Roger Merchberger]

On 11/23/2010 05:14 AM, Little John wrote:
> ----- Original Message ----- From: "Rogelio Perea" <os9dude at gmail.com>
>
>> Recently restored a 26-3004A F board CoCo, machine came with Color
>> Basic 1.2
>> only.
>>
>> Looking for a 24 pin ECB ROM chip to upgrade the machine.

> Rogelio,
> I'm not sure where to find those 8K 24-pin motorola EPROMs, but the
> TMS2564 claims to be compatible with it's 24-pin counterparts by
> allowing the extra 4 pins to "overhang" the socket. I will examine the
> datasheets in a bit to see if this is true - if it is, I could burn a
> TMS2564 for you. -JohnT-

If the 24-bit 8K EPROMs you speak of are model numbers MCM68764/68766, I 
have some good news & bad news...

Good news is:

1) I have what's commonly known as a "Metric Buttload" of them; I 
received a bulk lot (I think ~15 kilograms would be considered bulk... 
;-) ) on ePay back when it was auctionweb...

2) I have a bulk eprom eraser that can erase 20+ chips at a time...

3) I have a programmer that can program these critters,

4) I'm not one to overcharge people because I have a lot of something 
nobody wanted 15 years ago...

Bad news is:

1) These were insurance ROMs for the Panasonic/Quasar HHC pocket 
computers. As such, they're in specialized carriers... there's a 
decoupling capacitor soldered directly to the power pins that would need 
to be removed and the pins carefully unbent from around the carrier and 
just as carefully straightened before they could be inserted into a 
"normal" ROM socket.

This is certainly possible, I've done it several times -- but it's a 
labor of love, surely! For someone to extricate 2 or 3 chips isn't that 
bad, but for me to extricate chips for lots (read: a couple) of people, 
I really don't have that kind of time.

2) My eprom programmer only runs under DOS, I have no computers that 
currently do. (I do have PC that will work, but getting DOS and XP to 
dual-boot will be an "interesting" task to get working, and I still have 
to figure out a decent "sneakernet" as my new PC has no floppy, but DOS 
doesn't use USB devices without a *lot* of heartburn...

3) No such thing as a "rush order." ;-) The chips are in my 3rd floor 
attic, and I may have time this weekend to go rummaging around & find 
them, but prolly another week to get re-set up for erasing / burning / 
etc, so a 2-3 week minimum ship time, give or take...

I've offered custom programming for folks as I made an adapter (made by 
wire wrapping the pins on 2 back-to-back wire wrap sockets) so I can 
program the chips without removing them from the carrier. The adapter's 
not 100% foolproof (as a fool built it to begin with, eh?) so people 
that did want that option, I generally "sell one, send 3" that way if 
one of the chips didn't program/verify right (about 5% of the time, a 
chip would verify correctly but not be programmed correctly, haven't 
figured that one out yet...) or if a leg did break during extrication, 
there would be a "Plan B" (and C) available.

Chips are cheap, the programming's pretty cheap, but if you do want me 
to do the extrication, *then* it gets expensive... ;-)

A word to the wise: A couple dental picks help a *lot* for unfolding the 
chip pins from the carriers.

Hope this helps!
Roger "Merch" Merchberger