[Coco] rom swap with eprom?

[Dave Philipsen]

Does the cartridge have only 28 pins but there are positions for 40 
pins?  Seems like I recall that may have been the case.  I guess they 
were really skimping when they tried to save money by not putting all 
the pins on the edge connector!

I would guess that the ROM you found inside is a house numbered part 
that is a mask ROM with pretty much the same pinout as a 68764/6.  I 
also think the generic name for such a mask ROM was 2364.  Check out  
Retro-Innovations' adapter here: http://store.go4retro.com/2364-adapter/ 
Just use the adapter and then you can use the much more available 2764 
EPROM instead.

Dave




On 1/12/2016 12:31 AM, Steve C. wrote:
> Thanks for that, it will be helpful. My main source of confusion at this
> point is the coco service manual, which has a layout of 40 cartridge
> signals, with a schematic on the next page showing 36 pins on the cartridge
> port. The cart itself has only 28 pins! I think I will concentrate on the
> chip end of the thing as per your reference link and ignore the edge
> connector confusion if at all possible.
>
> On Mon, Jan 11, 2016 at 10:24 PM, Barry Nelson <
> barry.nelson at amobiledevice.com> wrote:
>
>> Try this information:
>>
>> http://ist.uwaterloo.ca/~schepers/sockets.html
>>
>> Even though this is for a Commodore computer, I have found the ROM pinouts
>> to be the same.
>>
>>> Steve C. towmater at gmail.com
>>> Tue Jan 12 00:58:13 EST 2016
>>>
>>> I bought a "Personal Finance" cartridge with the intention of swapping
>> the
>>> rom chip inside with a Drivewire eprom, but upon opening the  cart I've
>>> found a 24-pin un-google-able motorola part number ca 1980. I will spend
>>> the hours searching for a schema on the web, but if anyone has a shortcut
>>> to knowledge about compatibility with 27xxx eproms with the shack's
>> chips,
>>> please chime in and save me some eyestrain!
>>>
>>> -Steve
>>
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>>