Article View: comp.sys.amiga.tech
Article #12295Re: Official Warnings...
From: Andy Finkel
Date: Tue, 18 Apr 1989 20:09
Date: Tue, 18 Apr 1989 20:09
23 lines
1462 bytes
1462 bytes
In article <3082@haven.umd.edu> brett@sylvester-tr.UMD.EDU (Brett S Bourbin) writes:
>
> In the Jan/Feb 1989 issue of Amiga-Mail, under the "Official Warnings
>to ROM-Jumpers, Structure-Hackers, and Others", it states that you should
>NOT use the TAS assembly instruction. What is the reason for this?
The 68000 makes a couple assumptions about instructions like TAS
(those of the read-modify-write type). One is that the 68000 controls
the memory bus. The other is that the read-modify-write cycle is atomic.
On the Amiga neither is necessarily true; the custom chips control
the memory bus, and read-modify-write may be interrupted.
So switch to the MOVEQ. You'll be happier. We'll be happier :-)
--
andy finkel {uunet|rutgers|amiga}!cbmvax!andy
Commodore-Amiga, Inc.
"There is no programming problem that cannot be solved by proper
"application of the Delete command."
Any expressed opinions are mine; but feel free to share.
I disclaim all responsibilities, all shapes, all sizes, all colors.
Technical Details
Message-ID:
<6621@cbmvax.UUCP>Path:
arc1-ca.pugleaf.net!utzoo!dptcdc!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!rutgers!apple!oliveb!amiga!cbmvax!andyReferences:
<3082@haven.umd.edu>Show Full Headers
Complete Article Headers
Path: arc1-ca.pugleaf.net!utzoo!dptcdc!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!rutgers!apple!oliveb!amiga!cbmvax!andy From: andy@cbmvax.UUCP (Andy Finkel) Newsgroups: comp.sys.amiga.tech Subject: Re: Official Warnings... Message-ID: <6621@cbmvax.UUCP> Date: 18 Apr 89 20:09:20 GMT References: <3082@haven.umd.edu> Reply-To: andy@cbmvax.UUCP (Andy Finkel) Organization: Commodore Technology, West Chester, PA Lines: 23