To:	opendos AT delorie DOT com
Date:	Mon, 3 Jul 2000 19:08:19 -0700
Subject:	Re: Of large disks (Was Re: Fw: PTS-DOS)
Message-ID:	<20000703.193645.-752193.1.domanspc@juno.com>
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From:	Robert W Moss <domanspc AT juno DOT com>
Reply-To:	opendos AT delorie DOT com

I hope some of this info swiped from 11ED of Upgrading and Repairing PCs
is if some help.

BOB "DOMAN" MOSS  -------Be a Chocoholic-------- 

Default cluster sizes for FAT12/16 are:

0MB to under 16MB              8 sectors or 4096 bytes                   
12-bit
16 through 128MB                4 sectors or 2048 bytes                  
  16-bit
129 through 256MB              8 sectors or 4096 bytes                   
 16-bit
257 through 512 MB           16 sectors or 8192 bytes                    
16-bit 
513 through 1024MB           32 sectors or 16384 bytes                  
16-bit 
1025 through 32768             64 sectors or 32768 bytes                 
 16-bit 

Even if the 2-byte cluster size field could contain the value indicating
64KB clusters, 
the maximum partition size would still be constrained.  The maximum
partition size 
would be limited by the field in the disk parameter block that specifies
the number 
of sectors per cluster.  This field is only one byte long and its value
must be a power 
of two. This makes its highest possible value 128 sectors, which equates
to a maximum 
cluster size of 64KB.  65,536 at 64K each equals a maximum partition size
of 4GB.

The effect of larger cluster sizes (for Bernie) on disk utilization can
be substantial.
A 2GB partition containing about 5000 files with average slack of
one-half of the 
last 32KB cluster used for each file, wastes over 78MB [5000 x (.5 x 32)
KB]  
of file space.  

Looking at the above you would say that 256MB or 512MB would be the best
sizes
for a partition, but a lot of new programs out there use more than 512MB
just to 
install the program, and then you have to set up a location for data
files.
In that case the best size would be the size required for the program
files and a 
separate 128MB partition for data files IMHO since there can not really
be an ideal
partition size.  Besides, most of the computer users out there in the
real world are 
not power users and care less about all this so they like to have as few
distractions 
as possible when using the computer. Most of them would prefer to have
only one 
drive to worry about.

On Mon, 3 Jul 2000 17:06:45 +0200 (MET DST) Bernie
<bernie AT hem DOT passagen DOT se> writes:
> Arkady wrote:
> >     FAT16 limit is an 2G (really 4G, but MS restricts cluster size 
> by 32K
> >instead of 64K).
> 
> On one partition yes. Jikes, 64K clusters - no wonder they 
> restricted it to
> 32K, 512MB partitions are perfect IMHO.
> 
All clusters in FAT32 OS are : 
0MB to under 260MB    512 bytes 
260MB through 8GB   4096 bytes 
8GB through 16GB     8192  bytes 
16GB through 32GB   16384 bytes 
32GB through 2TB      32768 bytes 

Here again you might want to have 260MB partitions for data files and 
8GB for program files.   

> > > Or have I completely misunderstood this?
> >
> >     Yes. FAT limited in size (FAT16 - 2G, FAT32 much more), but 
> not in
> >position, which can be higher 8G.
>

I'm not a professional programmer myself but I believe it would take a 
"fairly long time" for a team of 10-12+ programmers working voluntarily, 
in their spare time, to write [from scratch] a program to emulate  or 
better the FAT 32 system.  This is not something to sniff at as even the 
great Bill Gates had to go out and buy a "Bootleg" copy of Digital
Research's
CPM which had been modified as a "quick and dirty" system to run on the 
Intel 80XX chips, that he then LEASED to IBM.  
 
One of the problems with OS's is the ability of the owner of the most
used 
OS to build into the system a few "dirty tricks" which make programs
crash 
when   another OS (DRDOS) is used to run the computer, hence one of the 
reasons for DRDOS's lawsuit against uncle Bill.
 Anyone wanting to sell a OS compatible with MSDOS has to pay 9 figure 
licensing rights fees to MS, but DRDOS wasn't invited to the party and
IBM 
was.  That's also one of the reasons Novell bailed out on DRDOS, even
though 
they still use it as a Boot system to start a computer with Novell
Networking 
NOS installed.  NDOS is not needed after bootup.

> Oh, how come only Windows95 can use that area then? I would assume 
> that
> other DOSes would be much more interesting if they could handle it 
> (I would
> change).


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