N* Lives!

Dave Dunfield dave09 at dunfield.com
Sat Apr 10 14:52:01 CDT 2010

>> The newest version of DOS on a DD image in your archives was 5.0.  I 
>> was hoping to somehow use 5.1 from a SD image, but it sounds like they 

No, according to my listings, I have the following versions of N*DOS for
the Horizon in the archive:

NSDOS20S  S     NorthStar DOS 2.0 Single Density (DOS only)
NSDOS40S  S     NorthStar DOS 4.0 Single Density
NSDOS51S  S*    NorthStar DOS 5.1 Single Density
NSDOS50D  D*    NorthStar DOS 5.0 Double Density
NSDOS51Q  Q*    NorthStar DOS 5.1 Quad Density (Unconfigured I/O)
NSDOS52Q  Q     NorthStar DOS 5.2 Quad Density
HORHD1B   D*    NorthStar HORIZON-HD System Diskette R1.B
HD221SD   Q*    NorthStar HDOS 2.2.0 H System Disk
HD221IRD  Q*    NorthStar HDOS 2.2.1 H Initial Recovery Disk
INSUA211  D*    INSUA NorthStar DOS 2.1.1 QuadDensity

S = Single Density (Single-Sided SD - 90k)
D = Double Density (Single-Sided DD - 180k) 
Q = Quad   Density (Double-Sided DD - 360k)
* = Image was made from original master diskette.

The 2.0 version I created from a disassembly by Barry Wazman - it has no
copyright date in the code, however the disassembly listing that Barry gave
included a statement that the original code was copyright 1977 N.S.C.

The 4.0, 5.1S and 5.0D have an embedded copyright date of 1978, and the
5.1DQ has an embedded copyright date of 1979. None of these have the "MOVER"
utility and appear to be fixed to run at $2000.

The 5.2DQ has an embedded copyright date of 1980, and does have the MOVER
program - I think this is the first version of N* DOS that can be positioned
to run lower in memory.

The INSUA release is the latest version of NorthStar DOS that I have, and has
an embedded copyright date of 1983 - clearly they were using a different version
numbering scheme. It can be configured for either double (1 side) or quad (2
sides) density.

>> issued multiple personalities for the different controllers - is that 
>> correct?

Yes, that is correct - the DOS version number has one or more letters
after the numbers:
  'S' = Single Density
  'D' = Double Density
  'Q' = goes with 'D', and means it supports Double Sided drives.

Note that you had to configure N*DOS to let it know which drives were double
sided (There's a table in the lower portion of the DOS image).

Also note that N* accesses double-sided disks differently than most everyone
else - instead of going side-0/side-1/side-0/side-1/... it accesses the first
half of the disk as the lower side, from outside to inside, and the top half
of the disk as the upper side, inside to outside. In other words, the lowest
numbered sectors on the disk are on the track-0 lower-side, and the highest
numbered sectors on the disk are on track-1 upper side.

Whats nice about this arrangement is that you don't have to do anything special
to access a single-sided disk - it's just smaller than a double, but the sectors
are in the same place. It also means that until you wrote enough data on a QD
drive to cross over to the top side, you could still read your files on a DD
drive. And finally, since N*s hard-sector controller does not need a formatted
disk, once you configured your drive for QD, you could simply write more data
to it than before. (The 'INIT' command just does a normal write of a blank
sector to every sector on the disk - this has the effect of setting up the
directory, and also prevents 'T1' errors of you try and read sectors you haven't
written yet).

And also note that N* was developed with the original SA400 35-track drives,
so by default there's only 35 tracks on a side (If you look at the early N*
disks, the "slot" where the head meets the media is shorter than on later
40 track disks. There were patches available to make use of 40 and even 80
track drives, but most "standard" N* disks (including all the ones in my
archive) are 35 tracks.


dave09 (at)    Dave Dunfield
dunfield (dot) Firmware development services & tools: www.dunfield.com
com            Classic Computers: http://www.classiccmp.org/dunfield/

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