[Coco] OS-9 and RS-DOS disk structures

[L. Curtis Boyle]

This is correct. It is the most efficient for seeking when reading contiguous files, since it stays on the same track and reads both sides without having to move the head.

L. Curtis Boyle
curtisboyle at sasktel.net



> On Dec 30, 2014, at 4:52 PM, William Astle <lost at l-w.ca> wrote:
> 
> On 14-12-30 03:39 PM, Allen Huffman wrote:
>> But I forget the format of double sided sectors for an OS-9 disk. Does it put the first 40 tracks (front side) then the next 40 tracks (back side), or does it interleave them top/bottom/top/bottom or something like that? I guess I never thought about the physical sectors/sides since OS-9 treated everything as Logical Sector 0 to MAX.
> 
> It alternates between sides:
> 
> Side 0, track 0
> Side 1, track 0
> Side 0, track 1
> ...
> 
> Most things that handle multiple sides do the same. This is where the notion of a "cylinder" comes from, referring to all instances of a particular track across all addressable sides. (You stack the tracks up and you get a cylinder.)
> 
> It does run through all 18 sectors on side 0 before going on to the 18 sectors on side 1 though.
> 
> 
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