Re: how do I use a snapshot card?

[dempson@actrix.gen.nz (David Empson)]

md <mdickins@brightok.net> wrote:

> I bought a snapshot card but I haven't a clue how to use it or really
> what it does.  It has a connector that looks like it might plug into
> the game socket on the mother board and a cord with a button on it.
> There is also a separate piece that looks like an empty chip socket
> similar to what might fit in the game socket, this piece really has me
> curious. 

That sounds suspiciously like the method used by genuine Apple language
cards to hook into the memory bus.

With a language card, there is a short ribbon cable with a 16-pin DIL
plug, that needs to be inserted in place of a RAM chip on the
motherboard.  The chip that is removed gets inserted into the empty
socket on the card.  The language card then makes use of the memory
refresh signals being generated by the motherboard to refresh its
on-card RAM.  In effect, it is just piggy-backing off one of the RAM
chips to get this information.

This only works with an Apple ][ or ][+, since later machines don't have
the same type of RAM.

I can't be certain that the same applies to this card, and I wouldn't
recommend experimenting without proper documentation.


I haven't seen a "snapshot" card, but I know that it is similar to a
"wildcard", which I did see once.

These cards work on the principle of taking a snapshot of the entire
memory contents and writing it out to disk.  This is done when you press
the button, which causes a non-maskable interrupt.  The card intercepts
the normal handling of the NMI by overriding motherboard memory
(particularly the ROM) and taking control of the CPU.

While in control, the entire memory is copied onto the card, then you
reboot and run software that lets you save the data to disk.

This is intended to be used as a deprotection method - once the
copy-protected software is loaded into memory, you can effectively save
it to a normal disk.  To run the software later, you simply BRUN the
file that was created by the card (or perhaps a front-end loaded, since
it wouldn't be able to load all of memory in one hit).

I suspect this particular card can only be used to capture software that
works in a ][ or ][+ and only requires 48K of RAM.  You would need the
software that went with it to be able to do anything useful.

-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand