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- Path: shell.portal.com!not-for-mail
- From: andy@shell.portal.com (Andy Finkel)
- Newsgroups: comp.sys.cbm
- Subject: Re: VIC20 cart grabbing
- Date: 5 Jan 1996 15:49:04 -0800
- Organization: Flying Cat, Inc.
- Message-ID: <4ckddg$g1s@jobe.shell.portal.com>
- References: <4ce84a$cpt@antares.lu.erisoft.se> <87ybrofltk.fsf@brushtail.hna.com.au> <87vimsi7hq.fsf@brushtail.hna.com.au>
- NNTP-Posting-Host: jobe.shell.portal.com
-
- In article <87vimsi7hq.fsf@brushtail.hna.com.au>,
- Chris Baird <cjb@brushtail.hna.com.au> wrote:
- >
- >It works-- and it's an old trick, one that even the authors of the
- >cartridges knew of (almost twenty years ago!), and hence why you'll
- >find Omega Race, et al., have extra code scattered throughout the
- >program which scribbles all over the ROM (now RAM) area. :)
- >
- >--
- >Chris,,
-
-
-
- It's more than just a trick vs ram carts ... its also an interesting
- programming trick. By shifting a rom memory location left or right you can
- test the state of the high or low bit easily & quickly, and branch on the
- result. Omega Race uses the trick, as does Radar Rat Race, and Sargon II
- chess. It's pretty funny running the programs from ram ... the rat race maze
- changes as you move, the chess program cheats, and your shots start zapping
- through memory in Omega Race.
-
- andy
-
- (author of Omega Race & Vic-20 Sargon chess)
- --
- andy@shell.portal.com
- "Like most veterinary students, Doris breezed through
- chapter 9, Equine Medicine" - G. Larson
- I disclaim all responsibilities. All shapes, all sizes, all colors.
-