[Coco] CoCo 2 64K upgrade blues

[Darren A]

On Fri, Aug 4, 2017 at 7:34 PM, Carlos Camacho wrote:

> I have a CoCo 2 with 16KB RAM. I decided to upgrade it to 64KB.
>
> Since I have a bunch of P21256-12 chips, I decided to go with them.
>
> <snip>
>
> It was recommended in the Facebook group that I ground Pin 1 to avoid
> memory issues as the machine is used.
>
> My first attempt, I connected each chip's Pin 1 to Pin 16. This didn't
> work.
>
> Next, I tried connecting all the Pin 1s together and go to ground on the
> motherboard. I tried to tap into the ground of the 6883 but it didn't boot.
>
> So, I tried to ground it on the RF box. It still didn't boot.
> <snip>
>


The CoCo 2 schematic I have (don't know if it's for the 8709416
motherboard) shows all the NC pin 1 of the DRAM chips are tied to +5V on
the board.  If you haven't lifted the pins out of their sockets and are
connecting them all to GND then you could be shorting out the whole system.

If the pins are all tied to +5V on the board rather than floating then
there is no need for any special mod, it should just work.


- Darren