Re: DSK to NIB Instruction

["Bryan Parkoff" <nospam@nospam.com>]

"Knut Roll-Lund" <kr-lund@nogarbage.online.no> wrote in message 
3YSdnSFo3q8SZdXeRVnzvA@telenor.com">news:3YSdnSFo3q8SZdXeRVnzvA@telenor.com...
> Paul Schlyter wrote:
>> In article <wc02f.8681$oc.149@newsread2.news.pas.earthlink.net>,
>> BluPhoenyx  <bluphoenyx-@-earthlink.net> wrote:
>>
>>>As for how to combine two .nib images, I don't know.
>>
>>  Why not simply try to concatenate the images?
>>  On a UNIX machine, you do like this:
>>  cat  image1.nib  image2.nib  >  combined_image.nib
>>  and in a Windows machine you do (from a command line):
>>  copy /b  image1.nib+image2.nib  combined_image.nib
>
> No! Have you tried this? A nib is 232960 bytes long and two times 143360 
> is 286720. This wouldn't work.
>
> The dsk format is sector contents directly 256 bytes times 16 sectors 
> times 35 tracks.
>
> The nib format seems to be each track as it would be seen by the drive 
> head that is 416 bytes times 16 sectors times 35 tracks. Sometimes it 
> seems that it is sectors still, not tracks, but some nib files seems to be 
> starting in the middle of a sector so it is probably tracks, even when 
> each sector is 416 bytes.
>
> So how does SST store this information... in the nib there is extra 160 
> bytes per sector. I don't know if it is this regular in SST's format. 
> There seems to be stored two tracks per on track original or maybe two 
> sectors per original sector. There is probably some header information 
> saying number of bytes etc.
>
> I would be interested in a tool that would do the opposite of the question 
> in this thread, to break a nib into two dsk images that can be used with 
> ADT and SST "unpack" on a real Apple. SST fails miserably in the emulators 
> doing this, to "pack" a nib into two dsk images. If someone would point 
> out an emulator where SST pack wouldn't fail that would also help.
>
> Maybe some source code for handling nib and dsk would enable me to 
> understand more.
>
> Knut
Hello,

    NIB format is the nibble character which it is to be individual bit as 
the stream binary.  It is true 4-4 encoding data and 6-2 encoding data.  It 
includes some information such as SYNC, header, and data.  SYNC is a group 
of 10 bits.  The last SYNC before header may have one group of 8 bits.  The 
header has volume information, track information, sector information, and 
checksum information.  Data has 6-2 encoding data including checksum.
    I can say that it contains approximately between 400 bytes and 1000 
bytes per sector.  It depends on space at random, but 500 bytes per second 
is very close because 500 bytes may vary between sectors.
    "Understanding the Apple //e" book and "Beneath to DOS 3.3 and ProDOS" 
book have full explanation how 4-4 / 6-2 encoding and nibble character work. 
"Beneath to DOS 3.3" does not have accurate information, but "Beneath to 
ProDOS" made the correction over earlier version of book in error.
    SST packs DSK image which it stores all nibble character information. 
The nibble size may vary.  There is only a way to locate header's track 
information and sector information before I append or capture to the 
blank.nib each sector until the number of sectors reach 560.  The 
blank.nib's size is 500 bytes for the first sector before appending until 
the size increases to be exact 232960 bytes.
    Do I explain clear?  It is what Apple II family reads NIB format and 
converts to a group of 8 bits as DSK format into memory for Apple II family 
to process.

Bryan Parkoff