Re: VIC-42

Hi Jim,

I don't have a spare 6500/1.  I just have one in a C900 keyboard but I do
have something similar from Zilog.

There are actually more than one manufacturer that makes "piggy-back" chips
for development.  These are used so you can just write out an EPROM and
drop it onto the chip so it acts as the internal ROM for the chip. You can
do this multiple times for a prototype until you are ready for production
chips.   I have a Z8613TS in both a ceramic package and a dip mini-circuit
board that shows you how some of the EPROM wires connect to the die.  It
doesn't help your 6500//1 requirement but it does help illustrate how it
works.  I have used these to low-level format Apple Profile hard drives as
it requires a special ROM to do so and that ROM was not public.

Here's a pic:
https://vintagecomputer.ca/wp-content/uploads/2021/06/Z8piggyback-scaled.jpg

Hope this helps,
Santo

On Thu, Jun 24, 2021 at 9:44 AM Jim Brain <brain_at_jbrain.com> wrote:

> On 6/24/2021 4:48 AM, Michał Pleban wrote:
>
> Frank Wolf wrote:
>
>
> Interesting! Can you post a picture?
>
> The piggyback Rockwell version is used in the Commodore 900 keyboard
> (photo courtesy of Jan Janssen):
> https://i.ibb.co/tZ2m68x/IMG-1538.jpg
>
> Regards,
> Michau.
>
>
>
> Hmm, someone wouldn't have a spare of these they'd be interested in
> discarding/selling/bartering?  I have truly never seen anything like that
> and I have this "must have one" desire at present.
>
> At the very least, it'd be nice to get more detailed pics from different
> angles.  Since the 6500/1 pinout does not match the 2716 at any point and
> that would not seem to make sense anyway, given the uC nature of the
> 6500/1, I am assuming the 2716 socket leads bend inwards and go to the die,
> but I've not before seen such a I am assuming that the leads for the 2716
> bend inwards and go into the ceramic case, but I don't see how leads would
> go through ceramic cases in that fashion.
>
>
> Jim
>
>
> --
> Jim Brainbrain_at_jbrain.com www.jbrain.com
>
>