[Coco] upgrading a CoCo 2 to ECB

[Roger Merchberger]

Rumor has it that Robert Gault may have mentioned these words:

>  Open up the Coco2. You should see two sockets or at least two in-line 
> solder points on the board. One is for the Basic ROM and the second is 
> for the Extended Basic ROM.
>  You don't replace the Basic ROM but add the new Extended Basic ROM. This 
> is the normal upgrade procedure which Tandy would perform.

Yes, but be warned - a bit of knowledge about different EPROM families is 
warranted here! Most people are accustomed to the 27xxx series of EPROMS, 
but their 8K EPROMS had 28-pins. On a CoCo the ROM sockets only have 24-pins.

If someone burns extended BASIC to a 2764, you/they will have to make a 
converter board to rewire the pins to the correct pinout.

The correct EPROM (as in: pin/level compatible) is the Motorola 68766 - a 
chip I just happen to have a metric buttload of. The problem with my chips 
isn't the pinout - it's the fact that they were in special carriers to be 
used in the Panasonic/Quasar HHC series of computers, and to use them in 
the carrier, you'd need to install a special socket for them (and they're 
made of unobtanium now - the only 2 I have cost me over $50 each, and that 
was nearly a decade ago!) so the pins will have to be manually unwrapped 
from the carrier & straightened (which can cause breakage if you're not 
careful) and a deglitching capacitor desoldered from the power pins before 
you could actually use the chip on the CoCo.

A word of advice to those willing to try extracting these chips - find a 
friend who's in the dental industry - dental picks are a definite help in 
this regard.

Thanks,
Roger "Merch" Merchberger

--
Roger "Merch" Merchberger   | Anarchy doesn't scale well. -- Me
zmerch at 30below.com.         |
SysAdmin, Iceberg Computers