Steven Hirsch wrote: I misread. A DD controller will only boot DD and the SD controller will only boot SD. The DD controller can read SD disks. Also there is such a thing as NS* dos being SD only as earlier version didn't know of the DD controller. I believe the DD controller came after V5.2. Memory says Morrow never bothered with NS*dos only CP/M but it tould be iteretesting to see otherwise. Allison

On Fri, 9 Apr 2010, Dave Dunfield wrote: Ok, that explains it! Thanks. 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 issued multiple personalities for the different controllers - is that correct? In other words, is the DOS file on that SD diskette targeted to SD controllers or can it be copied to a DD diskette and booted from there? Finally: If I install a double-sided drive, will my present DD controller support the "quad" density diskettes? The schematic shows the side-select line being brought out, and the docs suggest that bootstrap works the same on QD and DD. Steve --

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