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Groups > comp.sys.apple2.programmer > #2152
| Newsgroups | comp.sys.apple2.programmer |
|---|---|
| Date | 2016-01-18 09:40 -0800 |
| References | <n7f0e9$rk9$1@dont-email.me> <1mh6lw9.wn5g0t17dttg9N%dempson@actrix.gen.nz> <n7gjd4$7cc$1@dont-email.me> <1mh7olt.19ztyff765eueN%dempson@actrix.gen.nz> <n7h3pv$an0$1@dont-email.me> |
| Message-ID | <c6d2cdff-75e0-4c77-aeb1-77e0577c9f36@googlegroups.com> (permalink) |
| Subject | Re: Understanding a little something about bank-switched RAM |
| From | michael.pohoreski@gmail.com |
On Sunday, January 17, 2016 at 2:18:12 PM UTC-8, ultramagnus_tcv wrote:
> On 2016-01-17 20:07:04 +0000, David Empson said:
> > This sequence should do the trick:
> >
> > C081
> > C081
> > D000<D000.FFFFM
> > C083
>
> I didn't think to do that, but I understand completely.
This is an *old* "cracking" technique on the Apple ][.
1. Copy ROM to the LC1,
2. Change the Reset Vector at FA62, so that it enters the monitor,
3. Reboot your 48K game,
4. Press Ctrl-Reset and now you access to the game code. :-)
5. Move high memory down into the graphics page
6. Reboot into DOS 3.3 which will over-write high memory
7. Write a little "shim" to "restore" (move) memory back UP from the graphics page into high memory (since you don't need DOS anymore)
8. BSAVE GAME
Later games would disable the LC, so hardware such as the "Wildcard", or "Replay" would generate a NMI to take a "snapshot" of memory.
Also, the //e "broke" this trick, people would use their custom EEPROM F8 rom ($F800..$FFFF) such as the famous "Freeze's ROM" which forced Ctrl-Reset back to the monitor instead of the game code which usually cleared memory.
More fun details can be found in:
Cracking Techniques 1984, #9
http://boutillon.free.fr/Underground/Deplombage/Cracking_Techniques/1984/1984.html#F09
WRITE ENABLE THE LANGUAGE CARD: $C081
$C081
COPY ALL ROM INTO CARD: D000<D000.FFFFM
CHANGE RESET ROUTINE TO JUMP TO
MONITOR: FA62:4C 59 FF
WRITE PROTECT,READ ENABLE CARD: $C080
Good times! :-)
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Understanding a little something about bank-switched RAM ultramagnus_tcv <mikew@thecomputervalet.com> - 2016-01-16 21:08 -0600
Re: Understanding a little something about bank-switched RAM dempson@actrix.gen.nz (David Empson) - 2016-01-17 18:54 +1300
Re: Understanding a little something about bank-switched RAM ultramagnus_tcv <mikew@thecomputervalet.com> - 2016-01-17 11:38 -0600
Re: Understanding a little something about bank-switched RAM ultramagnus_tcv <mikew@thecomputervalet.com> - 2016-01-17 11:39 -0600
Re: Understanding a little something about bank-switched RAM dempson@actrix.gen.nz (David Empson) - 2016-01-18 09:07 +1300
Re: Understanding a little something about bank-switched RAM ultramagnus_tcv <mikew@thecomputervalet.com> - 2016-01-17 16:18 -0600
Re: Understanding a little something about bank-switched RAM dempson@actrix.gen.nz (David Empson) - 2016-01-18 15:42 +1300
Re: Understanding a little something about bank-switched RAM "Bill Garber" <willy46pa@comcast.net> - 2016-01-17 22:27 -0500
Re: Understanding a little something about bank-switched RAM ultramagnus_tcv <mikew@thecomputervalet.com> - 2016-01-18 10:53 -0600
Re: Understanding a little something about bank-switched RAM ultramagnus_tcv <mikew@thecomputervalet.com> - 2016-01-18 10:50 -0600
Re: Understanding a little something about bank-switched RAM michael.pohoreski@gmail.com - 2016-01-18 09:40 -0800
Re: Understanding a little something about bank-switched RAM ultramagnus_tcv <mikew@thecomputervalet.com> - 2016-01-18 17:23 -0600
Re: Understanding a little something about bank-switched RAM michael.pohoreski@gmail.com - 2016-01-19 23:05 -0800
Re: Understanding a little something about bank-switched RAM ultramagnus_tcv <mikew@thecomputervalet.com> - 2016-01-20 10:06 -0600
Re: Understanding a little something about bank-switched RAM michael.pohoreski@gmail.com - 2016-01-17 05:09 -0800
Re: Understanding a little something about bank-switched RAM ultramagnus_tcv <mikew@thecomputervalet.com> - 2016-01-17 18:36 -0600
Re: Understanding a little something about bank-switched RAM "Bill Garber" <willy46pa@comcast.net> - 2016-01-17 11:45 -0500
Re: Understanding a little something about bank-switched RAM dempson@actrix.gen.nz (David Empson) - 2016-01-18 09:07 +1300
Re: Understanding a little something about bank-switched RAM "Bill Garber" <willy46pa@comcast.net> - 2016-01-17 15:33 -0500
Re: Understanding a little something about bank-switched RAM michael.pohoreski@gmail.com - 2016-01-18 09:30 -0800
Re: Understanding a little something about bank-switched RAM dempson@actrix.gen.nz (David Empson) - 2016-01-20 18:17 +1300
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