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From: scotty@l5comp.UUCP (Scott Turner)
Newsgroups: comp.sys.amiga
Subject: Re: Reading Mac disks on the Amiga.  The Answer is...
Message-ID: <161@l5comp.UUCP>
Date: Fri, 29-May-87 14:52:39 EDT
Article-I.D.: l5comp.161
Posted: Fri May 29 14:52:39 1987
Date-Received: Sun, 31-May-87 19:36:15 EDT
References: <8705221955.AA05310@cogsci.berkeley.edu> <6938@amdahl.amdahl.com> <148@l5comp.UUCP> <1026@ark.cs.vu.nl>
Reply-To: scotty@l5comp.UUCP (Scott Turner)
Organization: L5 Computing, Edmonds, WA
Lines: 28
Summary: Mac uses a CRC not a checksum.

In article <1026@ark.cs.vu.nl> kleef@cs.vu.nl (Patrick van Kleef) writes:
I'm posting this public so that others won't think the answer has been found.
ie PLEASE use E-Mail to respond on this topic. I'm all for public discussion
but having to clean out discussions in other newsgroups on my un*x machine
(I LOVE cleaning the ST groups ;) I can see how other system admins might object
to all the data flow in our newsgroup.

>This information can hardly be passed thru this sort of medium.
I don't see why it can't?

>Go read Beneath Apple ProDOS or Beneath Apple DOS (Quality Software).
>Both books contain detailed information on how data is stored
>on Apple disks. Although both concern Apple ][ disks (DOS 3.3 and ProDOS),
>they will prove helpful, because the Mac also uses the same
>diskcontroller the Apple ][ uses and maintains the same 'raw' diskformat.
I've already read both works (many moons ago). And they are both excellent
books for the Apple ][ series. BUT...

You are incorrect about the Mac maintaining the same raw diskformat. In addition
to having 512 byte sectors (the apple ]['s use 256 byte) they also have those
sector tags for storing file system recovery info in. And worst of all the
Mac uses a CRC rather than the simple checksum used on the Apple ]['s.

Scott Turner
-- 
L5 Computing, the home of Merlin, Arthur, Excalibur and the CRAM.
GEnie: JST | UUCP: stride!l5comp!scotty | 12311 Maplewood Ave; Edmonds WA 98020
If Motorola had wanted us to use BPTR's they'd have built in shifts on A regs
[ BCPL? Just say *NO*! ] (I don't smoke, send flames to off
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