[Coco] Technical OS9 Q.

[Gene Heskett]

On Monday 23 January 2006 01:42, Bob Devries wrote:
>If a hard disk for OS-9 is formatted with two sectors per cluster, and
> the IT.SAS for the drive is set at, say, 32, does that mean that 64
> sectors will be allocated per directory when they are created?
>Does anyone here have a disk that's formatted this way, that could
> check this out?
>What are the usual DD.BIT and IT.SAS combinations?

Back when I had the 125meg scsi maxtor, that allowed 1 bit/sector 
formatting as the limit is a few bytes over 132 megs for a one 
sector/cluster format, so my experience was gained using 720k floppies 
as the test bed when I restored the multisector clusters abilities to 
rbf.mn all those years ago now.

Your assumption is correct only if you assume its IT.SAS at 2 sectors 
per bit.  That is not the case.  I don't recall in my experiments that 
the actually allocated number of sectors for a directory grew.  
Instead, the number of bits in the BAM that an 8 sector dir took up was 
reduced from 8 to 4.  Extend that in powers of 2 for big drives at up 
to 8 sectors/cluster.  Beyond that of course the directory allocation 
would grow to be whatever sectors/cluster was set to.  And to be 
truthfull, I did not explore at more than 8 when doing that testing.  
As drives have grown, I think its something that should be investigated 
now.

Bear in mind also that I was hand creating these multisector clustered 
test disks with ded after formatting these disks as format itself was 
not at that time, capable of doing the required manipulations.  Since 
it took about an hour per cluster size checked before the real tests 
could commence, and several hours to do the checking of the various 
functions, that was the other reason I didn't push on to 16 and 32 or 
64.

That said, I've historically had the IT.SAS set at $20 for hard drives, 
and at $10 for floppies as that usually results in a one contiguous 
group of sectors for the directory, which is extremely helpfull when 
patching up a bad filesystem with ded, something I became fairly 
proficient at when I was running my first hard drive interface, a B&B 
which had the rather nasty habit of handing rbf.mn an empty zeroed out 
buffer for a sector of the BAM.  You can logicaly extend the results of 
that into dcheck error report outputs of several hundred lines.  And it 
often happened 2 or 3 times an evening.  When I finally got the disto 
scsi setup, I was genuinely in hog heaven because it never made such 
mistakes.  At that point, I could actually code and enjoy it because 
all the mistakes were mine!

>--
>Regards, Bob Devries, Dalby, Queensland, Australia
>
>Isaiah 50:4 The sovereign Lord has given me
>the capacity to be his spokesman,
>so that I know how to help the weary.
>
>website: http://www.home.gil.com.au/~bdevasl
>my blog: http://bdevries.invigorated.org/

-- 
Cheers, Gene
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