Inside Commodore DOS [PDF]

Richard Immers and Gerald G. Neufeld:
Inside Commodore DOS : the complete guide to the 1541 disk operating system.
Northridge, Calif. : Datamost, 1985.
ISBN 0-8359-3091-2

(512 pages, 7.4 MB PDF)

In my quest to preserve retrocomputing documents, here is the invaluable book “Inside Commodore DOS”, which describes most of the internals of the Commodore 1541 disk drive. The scanning was done in 2002 by Kenneth S. Moore, who in 2005 released an OCRed version, which unfortunately replaced the original page images. My version here comes with the original page images and a table of contents, and is nevertheless fully searchable.

Here is a fun quote from the book by the way:

Over the years numerous writers have advised Commodore owners not to use the save and replace command because it contained a bug. Our study of the ROM routines and a lot of testing has convinced us that the bug in the replace command is a myth.

Of course, this is wrong. Don’t use “SAVE@” on a 1541.

12 thoughts on “Inside Commodore DOS [PDF]”

  1. Ah, yet another book that condems B-R and B-W because the authors didn’t understand what the commands actually do – they’re not meant to do the same thing as U1/U2. The only accurate description I’ve seen is in the original Commodore manuals, the only program I’ve seen that uses them is Pirates! (could be a feature specific to the ESI crack) which stores some of its texts directly in disk sectors and relies on B-R to get the length right.

  2. The 1541 manual has a really crappy explanation of B-R and B-W, and doesn’t really explain how they work – you have to read the section on U1/U2 and try to figure out what they do. The 1571 and 1581 manuals are better.

    B-R and B-W are pretty useless though, and U1/U2 are almost always what you want.

  3. Kudos! Great job! I used the scanned version before and had to correct it as the pages were mixed and duplicated but never made it to make it searchable.

  4. I’m glad to see the version I scanned for everyone many years ago has had work done to it to improve it.. At that time I just didn’t have the time to work more seriously on it, but I wanted people to have an electronic copy to refer to.

    Ken Moore

  5. This is very enlightening, but it’s extremely unclear as to *what* it fast-loads. How do I control what PRG it loads next? Also, could we have a compile-time option to switch the screen off and blast raster bars to the screen?


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