[Coco] NitrOS-9 floppy images

[Gene Heskett]

On Saturday 04 April 2009, Roger Taylor wrote:
>To whomever this concerns: the NitrOS-9 .dsk images have a porn link
>embedded in the boot track.  I just built a fresh boot disk with my
>own 6551 boot module and discovered that the links were copied across
>somehow, right after my boot module.  In fact, the link is repeated 7
>times, making it very obvious.

In which case it won't boot because that would make the boot track longer than 
the track is, which is 4608 decimal bytes, $1200 hex. That is not in the boot 
tracks I've ever generated.  There are a few bytes that aren't readily obvious 
as to what they do, one being the first (4?) bytes of the track, which IIRC 
contain the characters OS followed by the exec address of the first module, 
that is for compatibility with the basic.  Then at the end of the track, 
supposedly beyond the end of the last of 3 modules, is a 4? (memory is gettin 
hazy) integer table of IRQ addresses that will when moved to high ram where 
this code runs, supplying the addresses in low ram that a given hardware 
interrupt is vectored to when the various IRQ's are asserted.  Those last 8 
bytes fill up the whole of track 34 on a floppy.  There may be a string of 
$39's (RETurns) between the crc of the last module and this table also.  
Anything that mucks with that will quite likely cause a crash at about the 
time you see the OS9, BOOT message.

How many bytes do these things occupy, and can you capture it?  If this is 
true, its a first in what, 29 years?

I'd be one of the first to tell you to disinfect your winderz box, but I won't 
say that till I've seen that generated 'bttrk' that mb generates when run as 
maybe the sourceforge code has been attacked.  My last dl of 3.2.8 is over a 
year old, and I know its clean.

You may have to modify the mb file you are using so that it (bttrk) is not 
automatically deleted when its done with it, thereby leaving it on the src 
disk so you can look at it easier. Both dEd and vfy are quite handy tools for 
this.

-- 
Cheers, Gene
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
It's easier to take it apart than to put it back together.
		-- Washlesky