Re: DOS 3.2, 3.3 and ProDOS GCR in RWTS

From	awanderin <awanderin@gmail.com>
Newsgroups	comp.sys.apple2
Subject	Re: DOS 3.2, 3.3 and ProDOS GCR in RWTS
Date	2016-01-10 23:00 -0700
Organization	A noiseless patient Spider
Message-ID	<m37fjgbqqd.fsf@gmail.com> (permalink)
References	<9e054763-c065-493a-8b57-1bc7abe93cd7@googlegroups.com> <8fa4554d-e86b-4f60-8282-39960a6834bd@googlegroups.com> <fa355c8c-64c2-4639-8beb-47ae827127d3@googlegroups.com>

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Frank Schnorbus <fandr76@aol.com> writes:

> On Saturday, January 9, 2016 at 9:58:29 PM UTC-8, fadden wrote:
>> On Saturday, January 9, 2016 at 9:24:36 PM UTC-8, Frank Schnorbus wrote:
>> > I am not a programmer, but I have been fascinated by the scheme
>> > used to write data to the disk.  Some time ago, for the fun of it,
>> > I wrote an Excel spreadsheet that converts 256 bytes of data to
>> > the 342 (plus 1 checksum) bytes written to the disk for ProDOS.
>> > The spreadsheet converts it back the other way also.
>> [...]
>> > Lately I thought it would be fun to write similar spreadsheets for
>> > DOS 3.2.1 (which covers back to DOS 3.1 and uses 5x3, producing
>> > 410+1 bytes), and for DOS 3.3 (which like ProDOS uses 6x2).  I
>> > think I have it done for 3.2.1, but I need to confirm my work!  I
>> > have an Apple IIc, but it is in a box, and I am so rusty on how to
>> > do something like this, especially with DOS 3.2, that it would
>> > take me weeks (or months).  Are there any experts here that might
>> > be able to help me?  I'd be so appreciative!
>> 
>> 
>> Interesting approach. :-)
>> 
>> FWIW, you can find the CiderPress implementation of 6&2 and 5&3
>> encoding here:
>> https://github.com/fadden/ciderpress/blob/master/diskimg/Nibble.cpp
>
> Thank you!  I see that you wrote it for both 6x2 and 5x3.  Not to
> sound helpless, but I really don't know how to implement this program.
> Obviously it's a language, I presume Basic.  Step by step, how can I
> make this run?
>
> Or, if it would be easier just to give me the fish (instead of
> teaching me how to fish), can you give me the 411 disk bytes using the
> 256 input bytes I posted above?  I'd like to know how to fish, but
> I'll be happy with either!
>
> Lastly, is the 6x2 encoding/decoding the same for DOS 3.3 and ProDOS?
> I haven't tackled 3.3 yet, but in my search travels I'm pretty sure I
> read that they are handled differently.  Both are 6x2, but the data
> arrangements are different.

6&2 encoding is the same for DOS 3.3 and ProDOS.  At higher levels, DOS
3.3 used 256-byte sectors and ProDOS paired sectors up to logically have
512-byte blocks, but that doesn't affect the on-disk formatting.

Do you have the book, Beneath Apple DOS?  It's available on-line as a
PDF and it describes the 5&3 decoding in sufficient detail that you
should be able to implement in Excel.  You figured out 6&2 so 5&3 is
really conceptually the same but the details differ.


-- 
--
Jerry    awanderin at gmail dot com

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Thread

DOS 3.2, 3.3 and ProDOS GCR in RWTS Frank Schnorbus <fandr76@aol.com> - 2016-01-09 21:24 -0800
  Re: DOS 3.2, 3.3 and ProDOS GCR in RWTS fadden <thefadden@gmail.com> - 2016-01-09 21:58 -0800
    Re: DOS 3.2, 3.3 and ProDOS GCR in RWTS Frank Schnorbus <fandr76@aol.com> - 2016-01-10 10:15 -0800
      Re: DOS 3.2, 3.3 and ProDOS GCR in RWTS awanderin <awanderin@gmail.com> - 2016-01-10 23:00 -0700
        Re: DOS 3.2, 3.3 and ProDOS GCR in RWTS Frank Schnorbus <fandr76@aol.com> - 2016-01-10 23:56 -0800
          Re: DOS 3.2, 3.3 and ProDOS GCR in RWTS awanderin <awanderin@gmail.com> - 2016-01-13 23:12 -0700
            Re: DOS 3.2, 3.3 and ProDOS GCR in RWTS Frank Schnorbus <fandr76@aol.com> - 2016-01-15 23:21 -0800
              Re: DOS 3.2, 3.3 and ProDOS GCR in RWTS Frank Schnorbus <fandr76@aol.com> - 2016-01-16 00:02 -0800
              Re: DOS 3.2, 3.3 and ProDOS GCR in RWTS awanderin <awanderin@gmail.com> - 2016-01-17 00:00 -0700
                Re: DOS 3.2, 3.3 and ProDOS GCR in RWTS ultramagnus_tcv <mikew@thecomputervalet.com> - 2016-01-17 09:55 -0600
                Re: DOS 3.2, 3.3 and ProDOS GCR in RWTS awanderin <awanderin@gmail.com> - 2016-01-17 23:29 -0700
                Re: DOS 3.2, 3.3 and ProDOS GCR in RWTS Frank Schnorbus <fandr76@aol.com> - 2016-01-18 07:08 -0800
                Re: DOS 3.2, 3.3 and ProDOS GCR in RWTS ultramagnus_tcv <mikew@thecomputervalet.com> - 2016-01-18 10:56 -0600
                Re: DOS 3.2, 3.3 and ProDOS GCR in RWTS Frank Schnorbus <fandr76@aol.com> - 2016-01-19 01:13 -0800
                Re: DOS 3.2, 3.3 and ProDOS GCR in RWTS awanderin <awanderin@gmail.com> - 2016-01-19 22:58 -0700
                Re: DOS 3.2, 3.3 and ProDOS GCR in RWTS Frank Schnorbus <fandr76@aol.com> - 2016-01-18 07:05 -0800
        Re: DOS 3.2, 3.3 and ProDOS GCR in RWTS fadden <thefadden@gmail.com> - 2016-01-11 09:30 -0800
          Re: DOS 3.2, 3.3 and ProDOS GCR in RWTS D Finnigan <dog_cow@macgui.com> - 2016-01-11 19:34 +0000
            Re: DOS 3.2, 3.3 and ProDOS GCR in RWTS scott@alfter.diespammersdie.us (Scott Alfter) - 2016-01-11 21:18 +0000
              Re: DOS 3.2, 3.3 and ProDOS GCR in RWTS Frank Schnorbus <fandr76@aol.com> - 2016-01-11 21:33 -0800
                Re: DOS 3.2, 3.3 and ProDOS GCR in RWTS gids.rs@sasktel.net - 2016-01-12 09:30 -0800
                Re: DOS 3.2, 3.3 and ProDOS GCR in RWTS Frank Schnorbus <fandr76@aol.com> - 2016-01-13 20:48 -0800
                Re: DOS 3.2, 3.3 and ProDOS GCR in RWTS ultramagnus_tcv <mikew@thecomputervalet.com> - 2016-01-14 16:36 -0600
                Re: DOS 3.2, 3.3 and ProDOS GCR in RWTS Denis Molony <denisbytezone@gmail.com> - 2016-01-15 20:09 -0800
                Re: DOS 3.2, 3.3 and ProDOS GCR in RWTS "Michael 'AppleWin Debugger Dev'" <michael.pohoreski@gmail.com> - 2016-01-18 10:06 -0800
                Re: DOS 3.2, 3.3 and ProDOS GCR in RWTS Denis Molony <denisbytezone@gmail.com> - 2016-01-18 11:14 -0800
                Re: DOS 3.2, 3.3 and ProDOS GCR in RWTS "Michael 'AppleWin Debugger Dev'" <michael.pohoreski@gmail.com> - 2016-01-19 23:09 -0800
                Re: DOS 3.2, 3.3 and ProDOS GCR in RWTS Frank Schnorbus <fandr76@aol.com> - 2016-01-15 23:29 -0800
                Re: DOS 3.2, 3.3 and ProDOS GCR in RWTS ultramagnus_tcv <mikew@thecomputervalet.com> - 2016-01-16 14:15 -0600
              Re: DOS 3.2, 3.3 and ProDOS GCR in RWTS Raymond Wiker <rwiker@gmail.com> - 2016-01-12 21:47 +0100
  Re: DOS 3.2, 3.3 and ProDOS GCR in RWTS "Michael 'AppleWin Debugger Dev'" <michael.pohoreski@gmail.com> - 2016-01-10 07:56 -0800
    Re: DOS 3.2, 3.3 and ProDOS GCR in RWTS Frank Schnorbus <fandr76@aol.com> - 2016-01-10 10:22 -0800

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