Re: [stella] Anyone Have Supercharger Mod Schematic?

Subject: Re: [stella] Anyone Have Supercharger Mod Schematic?
From: Joe Grand <jgrand@xxxxxxxxxxxxxx>
Date: Mon, 04 Mar 2002 22:16:10 -0500
Here are 3 files that I believe were all on Bob's page..

sc.gif is a better quality (and color :) version of what Lee just sent to the list.. superch.gif is a reverse-engineered schematic of the Supercharger, and scmod.txt is Bob's description of the Supercharger mod..

I figure it's good to have these archived somewhere, which is why I attached them.. They're small enough, too.


At 06:36 PM 03/04/2002 -0800, Lee wrote:
Here ya go :- )

I took it off the WTW manual.
I'm sure Bob has a better pic somewhere.

BTW: The 74HCT32 chips are no longer available from Radio Shack. Check your local electronics
Explanation of Supercharger modification:

    The Supercharger has 3 banks of RAM, each containing 2 kilobytes.  The
Atari can directly address 4k of RAM, so only 2 of the 3 banks in the
Supercharger can be accessed at any given time.  To access the third bank
of RAM, it must be "bank-switched" with one of the banks currently being
addressed.  Since there is no hardware built into the Atari to tell the
Supercharger to switch banks, the Supercharger has to use something to
trigger the switch.  The Supercharger "watches" the memory locations being
addressed inside of it, and if it "sees" that location $FFF8 has been
accessed, it switches the memory banks.  There is a little bit more to it
than the preceeding explanation, but that should be enough for you to
understand how this modification works.

    The goal of the modification is to disable the circuitry that watches
for the $FFF8 location to be addressed (it may also watch for $FFF9, but
this modification takes that into account).  The problem is that the
circuitry must be active while the game is loading, because once the game
is loaded, the Supercharger must switch from the ROM program stored in
itself to the new code just loaded.  Fortunately there is a trigger in the
Supercharger that you can activate once the game is loaded (My makewav
program does this).  So now all we need to do is to use that trigger to
disable the circuit that watches $FFF8.  That is exactly what this
modification does.

    The address of $FFF8 is the binary equivelant of:

                    1111 1111 1111 1000

Each one of those 1's and 0's is attached to the circuit watching for $FFF8.
What my modification does is wait for the trigger to activate after a game
loaded, and then disonnect the wire watching the second zero from the right
in the binary sequence above.  In it's place, it puts a 1 so that when the
address $FFF8 is accessed, the watcher sees:

                    1111 1111 1111 1010

and goes upon it's merry way, never suspecting that $FFF8 was accessed!

Here is the circuit in electronic symbols:

                         (toggle switch)

(modified mode)    Trigger ___    ___ Ground    (normal mode)
                                |    ___
                                |___|   \
                                    |OR |_____ (A1) of watcher circuit
       (A1) in Supercharger ________|   |
When the toggle switch is in the (normal mode) setting, the Supercharger
acts as it normally would without modification.


Besides the fact that I take no reponsibility for any damages done to your
Supercharger, Atari (or compatible), TV, room, house, neighborhood, cat,
dog, etc... resulting from any attempts made to make this modification,
you need to be aware of one more thing:

    IF you are brave enough to try this and
    IF you succeed then:


    Did I make my point?  If you try to play a multi-load game with the
toggle switch in the (modified mode) position, when it comes time to make
second load, the game will most likely crash!

    Oh yeah, DON'T flip the switch while your Supercharger is on, turn off
your Atari (or compatible), flip the switch, then turn the Atari back on.

                        Have FUN!

                                Bob Colbert

Attachment: sc.gif
Description: GIF image

Attachment: superch.gif
Description: GIF image

Current Thread