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Emulator Debugging: Area 5150's Lake Effect

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My last few   articles on bus sniffing the IBM 5150 have been building up to this one. We're going to leverage our bus sniffer and sniffer decoder to finally debug Area5150's "Lake" effect. "But wait -", you might be asking: "- doesn't MartyPC run Area5150 already?" Yes, it does, but I have a dirty little secret I need to confess to the world.  Despite all the accolades MartyPC has received about being super-accurate, it needed a special, Area5150 specific hack in order to run the final two cycle-counted effects, "Wibble" and "Lake."  "Wibble" is the scene with Charlie Chaplin, the green fellow and the elephant.  "Lake" is the final end credits scene with the water effect and the PCM audio player.   In other words, I cheated. It haven't actually tried that hard to keep it hidden, as you can see if you are watching the console while MartyPC runs: Okay, maybe I'm being a bit hard on myself. Title-s...
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PC Floppy Copy Protection: EliaShim CodeSafe

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This is part 6 of a series of articles investigating various floppy copy-protection schemes seen on the IBM PC platform. You may wish to read the previous entries in this series: Part 1, covering Formaster Copy-Lock Part 2, covering Softguard Superlok Part 3, covering Electronic Arts Interlock Part 4, covering Vault Prolok Part 5, covering XEMAG Xelok EliaShim Microcomputers was a computer technology firm based in Haifa, Israel, with a US-based office in Tampa, Florida. From 1983 to the early 1990's they marketed a number of copy-protection technologies under the CodeSafe trademark .  By the 90's these mostly included various dongles, with the age of floppy-based protections drawing to a close.   EliaShim, unlike many of the companies we've covered, would more or less successfully pivot to different market in the mid 90's. EliaShim ViruSafe, an anti-virus product for DOS, Windows 3.1, 95 and NT, saw moderate success, enough to get EliaShim  acquired by Aladdin Knowle...
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PC Floppy Copy Protection: XEMAG Xelok

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This is part 5 of a series of articles investigating various floppy copy-protection schemes seen on the IBM PC platform. You may wish to read the previous entries in this series: Part 1, covering Formaster Copy-Lock Part 2, covering Softguard Superlok Part 3, covering Electronic Arts Interlock Part 4, covering Vault Prolok XEMAG was a commercial disk duplicator that provided services to companies such as Electronic Arts, Activision, IBM, Ashton-Tate, and Oracle. XEMAG traces its origins to the disk duplication department of Peripheral Marketing, Inc., from which it was spun-off in 1983. By 1983 they were duplicating a million floppies a month.  Reproduction of a design appearing on some XEMAG swag   For some background into what working at XEMAG was like, you may wish to read  this interview with Peter Brown, a former XEMAG employee. XEMAG was acquired by the Xidex Magnetics Corporation  in February of 1983, for $3.78 million . Xidex would then acquire disk manufac...
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