[Coco] OS-9 sector allocation bitmap AKA LSN 1

[Christopher Hawks]

Willi Kusche said the following on 09/02/2012 06:38 PM:
> Hi!
>
> On Sun, Sep 2, 2012 at 7:04 PM, Gene wrote:
>> You may in fact have found a bug, but I wonder if its worth fixing.  My
>> system isn't up at the moment, but I assume one could clear that bit with
>> dEd of bd, and then check to see if it triggers anything, or is even
>> reported by free.  I really don't know, never having noticed that.
>
>      It would be interesting to see if that bit is set in the
> allocation bitmap on a freshly formatted disk.  Also, I need to look
> at the actual sector that bit refers to, to see if common data exists
> there on multiple disks.
>

Willi:

	You didn't specify what size disks. On a freshly formatted CoCo disk (35 
tracks, single sided), the least 2 bits in the last byte of the allocation map 
are set. That is because 35 tracks * 18 sectors per track (630 sectors) / 8 
bits per byte is 78.75 bytes (or 0x4E bytes and 6 more bits). So byte 0x4e 
('cause we're 0 based) of the allocation map = 0x03.

	What size are Apple 0S9 disks??


-- 
Christopher R. Hawks
HAWKSoft
------------------------
 > Linux is not user-friendly.
It _is_ user-friendly.  It is not ignorant-friendly and idiot-friendly.
	-- Seen somewhere on the net.