Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!bbn!apple!amdahl!shs
From: shs@uts.amdahl.com (Steve Schoettler)
Newsgroups: comp.arch
Subject: Re: address masking gimmick
Message-ID: <18GrQ67TYS1010AnbJM@amdahl.uts.amdahl.com>
Date: 12 Apr 89 19:53:48 GMT
References: <28200296@mcdurb> <11271@tekecs.GWD.TEK.COM>
Reply-To: shs@amdahl.uts.amdahl.com (Steve Schoettler)
Organization: Amdahl Corporation, Sunnyvale CA
Lines: 22

In article <11271@tekecs.GWD.TEK.COM> andrew@frip.wv.tek.com (Andrew Klossner) writes:
>[]
>
>	"Time yet again for expression of one of my favorite
>	architectural "gimmicks": provide a mask that is implicitly
>	ANDed with any {instruction,data} address before use

In the early masks of the Rockwell 6502, unimplemented opcodes were not
trapped, and often did some crazy things.

One of the "reserved" opcodes performed  X & PC -> SP.

Maybe they were before their time :-).

Steve

-- 

        Steve Schoettler
        shs@uts.amdahl.com
        {sun,decwrl,pyramid,ames,uunet}!amdahl!shs
        Amdahl Corp., M/S 213, 1250 E. Arques Ave, Sunnyvale, CA 94088