[Coco] Clustering a HD

[Robert Gault]

Bob Devries wrote:
> Hello all,
>
> I'm "playing" with OS9/68000 on my Atari STe. The version of OS9 is V2.3, which has a number of limitations. Since I have a copy of V2.4, I thought I'd try to "upgrade" the Atari OS9, but that's not my question.
>
> How large can a hard disk be before it is necessary to change the cluster size? I believe that this relates to OS-9/NitrOS9 as well as OS-9/68000. I believe it's ~128MB; can someone verify that?
>
> Regards, Bob Devries
> Dalby, QLD, Australia

It's probably more a personal preference than anything else. There is a physical 
limit imposed by the number of sectors addressed in the allocation map. In 
NitrOS-9/OS-9, the allocation map is limited (DD.MAP = 2 bytes) to $10000 bytes 
which is thus $80000 clusters or $80000 sectors with DD.BIT=1. At 256 bytes per 
sector, that's about 134Meg.
Of course that means 256 sectors in the map which you might consider a waste of 
sectors.

You are also limited in OS-9 to $1000000 total sectors as DD.TOT is 3 bytes.

Robert