Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uflorida!haven!umd5!hans
From: hans@umd5.umd.edu (Hans Breitenlohner)
Newsgroups: comp.sys.atari.8bit
Subject: Re: More on SIO
Message-ID: <4779@umd5.umd.edu>
Date: 28 Apr 89 19:56:58 GMT
References: <38936@bbn.COM>
Reply-To: hans@umd5.umd.edu (Hans Breitenlohner)
Organization: University of Maryland, College Park
Lines: 21

In article <38936@bbn.COM> slackey@BBN.COM (Stan Lackey) writes:
>  ... read sectors 1,2,3
>of an Atari disk (which, by the way, Atari keeps in SD.  Question 1.
>Is that done by software in the computer, or by the drive itself?)

The sectors on the disk are actually 256 byte double density sectors.  
The drive only transfers the first 128 bytes from/to the computer.

>
>As I recall, when I used Spartados DSDD XF551, it seems those sectors
>may have been formatted DD because it took a couple "tries" before
>a DD would boot.  Question 2. Does anybody know?
>
I think these problems are related to the drive not recognizing (at least not
until it gets several errors) that the disk is double sided.

>Finally.  I still can't read PC-DOS disks.  Are they in 256-byte sectors?

No, 9 512 byte sectors per track.
A slight additional complication is the fact that all Atari formats write
the complement of the data to disk.