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From: danm@mspiggy.UUCP
Newsgroups: net.micro.6809
Subject: OS/9 device driver omission
Message-ID: <110@mspiggy>
Date: Thu, 27-Oct-83 20:32:25 EST
Article-I.D.: mspiggy.110
Posted: Thu Oct 27 20:32:25 1983
Date-Received: Mon, 31-Oct-83 09:55:29 EST
Organization: Microsoft, Bellevue, WA
Lines: 33

In trying to write a device driver for a hard disk on my CoCo under
RS's version of OS/9 (Microware version 1.2), I kept getting access
permission errors (#203, I believe).  I called RS about this (their technical
hotline is (817) 390-3944).  They were unable to help me.  So I
called Microware.

It turns out that the RS documentation omits to mention that you need
to include the access code in the device driver ** as well ** as the
device descriptor.  This access code should immediately follow the MOD
statement that begins the device driver code.  This is the same code that
the device descriptor uses.  Without this code in both modules, you
will get access permission errors.

Another interesting fact that I learned is that RS V1.00 (as well as
Microware V1.2) place no restrictions on sector allocation map size.
This means that if you are using disks with capacity greater than 1M,
no special provisions need to be made for that.  The RS documentation
states that the size of the sect. alloc. map must be less than 4096 bits.
To handle large disks, you grouped sectors into clusters, with the
number of sectors per cluster being specified in the device descriptor.
Unfortunately, this is an artifact of Microware OS/9 V1.1 and earlier.
This restriction doesn't apply to RS OS/9.  This field is ignored by
FORMAT and the rest of the software (actually, FORMAT sets it to 1
in sect 0, track 0 and calculates the rest of the parameters correctly).
The result is that you can ignore that actual value of this field (but
make sure you reserve space for it in the descriptor).

Hope this helps anyone else who has had dev driver problems,

				Happy hacking,
				Dan McCabe
				decvax!microsof!danm