[Coco] Seeking: ECB ROM chip

[Little John]

----- Original Message ----- 
From: "Roger Merchberger" <zmerch-coco at 30below.com>
To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
Sent: Tuesday, November 23, 2010 11:51 PM
Subject: Re: [Coco] Seeking: ECB ROM chip


> 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
> 
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