[Coco] Glenside IDE problem

[Gene Heskett]

On Wednesday 10 December 2014 19:57:32 Bill Pierce via Coco did opine
And Gene did reply:
> Gene, it's still going... about the 5th time through the format display
> code LOL It's a 4 gig partition.

4Gb, that may be the limit of the drive os9 can handle as its sector 
address, a 3 byte hex integer, hits the FAT full and end of its math 
ability at $FFFFFF. At 1 sector per cluster, the max drive size is 
134.217,728 Mbytes.

At 2 sectors per cluster, you can get to 268.435,456 Mbytes when the FAT
is full. You can only increment this in powers of 2, so a 4 sector cluster 
allows a 536.870,912 Mbyte drive. 8 gets you to 1.073,741,824 Gbyte drive.

Next step is 16 sector clusters, and gives a 2.147,483,648 Gbyte drive.

Then 32 gives a 4.294,967,296 Gbyte drive.
But the address passed from RBF to the drivers tops out at $FFFFFF, and 
that is sectors, not clusters, but some more kcalc button clicking says 
that has also hit the limit at that same 4.294,967,296 Gbyte drive size.

You might get away with it.  It's been going on a couple decades since I 
last walked into RBF and kicked the tires and Boisy, maybe others too, 
have been there after me, so lets hope that there are not any signed math 
operations in how it does it, but that could cause it to fall over at the 
2Gbyte point.

But consider this: At 32 sectors per cluster, you could open a file for 
writing, and write 8192 bytes before it would have to go back to the FAT 
and allocate another bits worth of space, another 8192 bytes, to that 
files allocation.  A bit mind boggling.  OTOH, one of my scsi drives is a 
gigabyte, running at 16 sectors per cluster, and appears to be working 
perfectly.

> Ack  kcalc thats only 11,263,744 byte into the drive.  That does seem a
> little slow.  How big is the drive?
> 
> Cheers, Gene Heskett
> 
> 
> 
> 
> 
> Bill Pierce
> "Today is a good day... I woke up" - Ritchie Havens
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Cheers, Gene Heskett
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