[Coco] upgrading a CoCo 2 to ECB

[Robert Gault]

Roger Merchberger wrote:
> 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.
 ><snip>

If the pinout for the Extended ROM is the same as the pinout used in a 
ROM pack or Disk controller, you don't need a converter board. Adapting 
the 28 pin 27xxx series to the 24 pin Pak/Controller is very simple and 
just requires several thin wires and perhaps lifting a pin on the EPROM.

I have the details somewhere and can post them is requested.