Date: Tue, 04 Feb 1997 12:17:51 -0600 (MDT)
From: Roger Ivie <IVIE AT cc DOT usu DOT edu>
Subject: Re: [opendos] OpenDOS + Win95 w/FAT32?
To: OPENDOS AT MAIL DOT TACOMA DOT NET
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david AT diablo DOT eimages DOT co DOT uk said:
> I said:
>> MP/M and CP/M 3.0 were a big problem. MP/M is a multiuser version of CP/M; 
>> it's larger than 6,656 bytes just for the parts distributed by Digital 
>> research...
> On my CP/M 3.0 system (yes, I still have it!) it has 512-byte sectors, 
> 9 per track.  That gives 9216 bytes in the two reserved tracks.  Of 
> this, 2048 bytes is used for the directory (64 entries of 32 bytes 
> each), giving 7168 bytes (7K) for code.  

Actually, the directory lives in the first cluster on the disk, not in
the reserved tracks. The BIOS reserves up to 16 clusters for the directory;
in your case, it sounds like one cluster is reserved. Since at least one
cluster is always reserved for the directory, CP/M can use the magic
number 0 to point to an unallocated cluster since you can't create files
which contain the directory.

With 16 reserved clusters each containing 16K bytes, the largest possible
directory on a CP/M machine can describe 8,192 files.

> Mind you, I don't boot off a floppy any more.  I've put the OS (along 
> with some patches for things like my serial port, 3.5" disks, etc...) 
> into ROMs.  

I didn't claim (this time :-) that we should all be running CP/M. I just
wanted to point out an interesting solution to the problem of getting the
OS loaded with not enough resources available to do the job the
straightforward way...

Roger Ivie
ivie AT cc DOT usu DOT edu