Date: Tue, 08 Jan 2002 15:36:12 -0800 From: "Bruce A. Mah" <bmah@FreeBSD.ORG> To: Matthew Dillon <dillon@apollo.backplane.com> Cc: Terry Lambert <tlambert2@mindspring.com>, D J Hawkey Jr <hawkeyd@visi.com>, freebsd-hackers@FreeBSD.ORG Subject: Re: Oh my god, Google has a USENET archive going back to 1981! Message-ID: <200201082336.g08NaCw78995@bmah.dyndns.org> In-Reply-To: <200201082314.g08NExK62190@apollo.backplane.com> References: <20.21dd4868.296bb1c2_aol.com@ns.sol.net> <3C3A810A.C616A903_mindspring.com@ns.sol.net> <200201081104.g08B4i309583@sheol.localdomain> <200201082138.g08LcFS61637@apollo.backplane.com> <3C3B7997.205E404A@mindspring.com> <200201082314.g08NExK62190@apollo.backplane.com>
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If memory serves me right, Matthew Dillon wrote: > But, do you know what '02' does? On an original 6502? The 6502 > was a hardwired processor, which means that even the hex codes that > didn't have an official instruction did things. Weird things to be > sure, but things nontheless. They cleaned it up later on (in the 816) > but not in the PET/C64 era and not on the 6502 based 65xx series. I'm not sure I've ever heard anyone ever call the 65816 a cleaned-up version of anything. Talk about a Jeckyl and Hyde processor! (For the uninitiated, it had these mode bits where you could set parts of the processor to be either 8-bit or 16-bit mode, along with things like the 8086's segment registers to give you this pseudo-24-bit addressing. I think they finally did use all 256 opcodes on that one.) Oh yeah, I think someone had to do some amount of "clean up" for the 65C02 since it had a few more (defined) opcodes than the original 6502. [Centipede game] Ob-65XXX hack: I once wrote a spreadsheet, starting from a numerics package, ProDOS, and a GUI toolkit. In assembler. Doing the infix expression parser was especially fun. If anyone remembers Pinpoint Publishing and their still-borne "Digit", well, that was it. I still have my code, in a couple of two-inch binders somewhere. > Somebody somewhere has a complete list of unsupported instructions > that nevertheless do interesting things. I have this odd feeling that such a list was either in the Zaks book or one of the Apple ][ reference manuals. Bruce. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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