Date   : Mon, 01 Jul 1985 19:41:20 GMT
From   : John Blalock <jb%terak.uucp@BRL.ARPA>
Subject: Re: CPM 2.2 maximum disk storage space (?)

> []
> I have a 10M byte hard disk running CPM 2.2.  When I have 8M bytes 
> worth of files on my disk and then create another file, the new file 
> overwrites my directory.  The maximum group number I could use is
> 7FFh (which corresponds to 8M bytes) and the new file is allocated
> group 0 which happens to be the directory area.
> 
> A CPM book that I have states that the maximum storage space CPM 2.2
> supports is 16M bytes.  Could somebody shed some light on this 
> discrepancy?
> 
> I would appreciate any help.
> 
> - Robert Ling.   <rling@uw-june>
The maximum storage space depends on the block size your BIOS uses.  CP/M
allows up to 64K blocks, each block can be 1, 2, 4, 8, or 16K as I recall.
An even more limiting feature (?) is only 16 blocks can be allocated to the
directory.  Assuming you use 2K blocks (32 MB disk capacity possible), you
can have only 1024 directory entries...

I hope this helps and, even tho I don't have the manuals here for reference,
I think the numbers quoted are reasonably accurate.  I'm currently in the
process of hacking up my BIOS to add a couple of 8 MB disks and remember
looking all this up in order to decide block size and determine my DPB.
It sounds like you have an improperly defined DBP if your directory is
getting wiped out.

John Blalock, W7AAY

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