[Coco] Another Coco Virtual Disk Util

Wayne Campbell asa.rand at gmail.com
Wed Oct 23 20:29:26 EDT 2013


Hi Robert,

I have heard of this before. Thanks for the refresher. I never went far
enough to test the limits of my system back then.

Wayne
 On Oct 23, 2013 11:35 AM, "Robert Gault" <robert.gault at att.net> wrote:

> Wayne Campbell wrote:
>
>> I may be mis-remembering something. I do recall that if I change the
>> cluster size it will affect how many sectors are used when allocating
>> space
>> for a file, or to increase the allocation for a file. The minimum is
>> 1-sector clusters, and over a certain size of drive space (I seem to
>> recall
>> it being $5A000) you cannot use 1-sector clusters.
>>
>> If someone knows what I am talking about, please feel free to correct me
>> or
>> back me up, whichever is required.
>>
>> Wayne
>>
>
> You can use 1 sector per cluster with almost any sized disk if you don't
> mind wasting an incredible amount of space in the OS-9 MAP. As you increase
> sectors per cluster (powers of 2) there is a tradeoff between effient use
> of the MAP and wasted space in the last cluster assigned to a file.
>
> And no there is no right answer. :) That choice is left up to the
> enlightened user of OS-9. Ha!
>
> More seriously, at some point the MAP can't indicate the number of used
> clusters. The MAP size must be indicated with 2 bytes DD.MAP so it can
> contain only $FFFF bytes or describe $7FFF8 sectors at 1 sector/cluster.
> There are similar problems with large hard drives that are limited by
> DD.TOT to $FFFFFF sectors.
>
> Robert
>
>
>
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