Path: utzoo!attcan!lsuc!ncrcan!brian From: brian@ncrcan.Toronto.NCR.COM (Brian Onn) Newsgroups: comp.arch Subject: Re: amusing opcodes Message-ID: <878@ncrcan.Toronto.NCR.COM> Date: 18 Aug 88 00:56:48 GMT References: <5458@ecsvax.uncecs.edu> <1876@looking.UUCP> <753@applix.UUCP> <3884@sequent.UUCP> <719@mcrware.UUCP> <5440@june.cs.washington.edu> <1988Aug7.013526.7798@utzoo.uucp> <217@mango.athertn.Atherton.COM> Reply-To: brian@ncrcan.Toronto.NCR.COM (The Super User) Organization: NCR Canada Ltd., Mississauga, Ontario Lines: 22 In article <217@mango.athertn.Atherton.COM> ericb@mango.UUCP (Eric Black) writes: >In article <1988Aug7.013526.7798@utzoo.uucp> henry@utzoo.uucp (Henry Spencer) writes: >>As is now moderately well-known, some of the Motorola 8-bit chips actually >>have such an instruction, sort of: there is a test opcode which makes the >>CPU just sit there endlessly incrementing its address lines. Nothing short >>of powerdown will shake it out of this. Some third-party opcode charts >>show this as HCF. The Motorola spec sheet that I remember doesn't give it >>a name, but does have a footnote warning you about it. > >Actually, it's better called WTD -- "Walk The Dog". On the 6800 it... Is'nt this (HCF) an acronym for Halt and Catch Fire?. I remember seeing it described as just that in one of those third party opcode charts. :-) Brian. +-------------------+--------------------------------------------------------+ | Brian Onn | UUCP:..!{uunet!mnetor, watmath!utai}!lsuc!ncrcan!brian | | NCR Canada Ltd. | INTERNET: Brian.Onn@Toronto.NCR.COM | +-------------------+--------------------------------------------------------+