Re: Hiding code from the User...

From: Professor Dredd (
Date: 2001-04-02 15:25:19

If you REALLY want to know the details of how these
devices install themselves into the system and where
their I/O is mapped, here is what I would do.

Get your trusty copy of Anatomy of the C-64 (Abacus)
and open it to the ROM disassy. Enable the cart/device
and start your monitor. Begin with the vector at $FFFC
and trace the power-up/reset routine. Use the Anatomy
disassy for comparison purposes.

One thing to keep in mind about RAMLink, RAMDrive and
other such devices is that they generally contain user
data. If you intend to program RAMLink's hardware
directly, you must make NO ASSUMPTIONS whatsoever
about the configuration or content of the device.
Otherwise your program may destroy data, or at least
make it unaccessable to the user.

--- wrote:
> Hi All,
> I was wondering if we could share what we each know
> about how various
> utility cartridges /expansions go about installing
> themselves on the C64 and
> them hiding from the User.
> For example:
> KCS Power Cartridge has a 6810 (128byte RAM) which
> is in the I/O area and
> vectors are routed through this to switch in /out
> the ROM expansion
> The FINAL Cartridge III mirrors 512 bytes of ROM
> into the I/O space for the
> same reason
> Other carts (eg freezers) use a combination of RESET
> and NMI to wedge
> themselves at the push of a button.... 
> But how to do some of the other devices work:
> RAMLINK (in particular where does RLDOS live)??
> Epyx FastLoad (there's only a ROM and logic here)??
> Action Replay (EPROMS, RAM and Logic)??
> How do the C128 carts do it?
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