Alfredo equates the Mac file system to the MPE/iX system in that they are
both 32bit based. It now seems the statement contained a few errors,
perhaps due to the enthusiasm Alfredo shows for Macs. For one thing,
MPE/XL had a 32 bit file system before 1987. In fact, I remember it being
so in 1986 when I first logged onto a 930 at the SEMC during that summer.
Now Bruce informs us the file system on Mac is still 16-bit based in the
allocation area. Bruce seems to have all the facts about the Mac file
system.
Let me add a few more facts about Windows. There are a couple utilities
which migrate FAT16 to FAT32 and back and also between the FATs and NTFS.
I use Partition Magic 3.0 myself, works fine, lasts a long time. FAT16
cannot deal with a PARTITION greater than 2 gigabytes, so the example of
4GB is a non-sequitur. My earlier missive explained in detail the
differences between FAT16, FAT32 and NTFS so I will not repeat it here.
Suffice it to say, that apart from people wanting to dual boot between
Windows 95 B (OSR2) and NT on the SAME machine, there is no reason to stay
away from FAT32. (I do not see someone wanting to dual boot between
Windows 95 and Windows 95B on the same machine, and anyways Windows 95B
disables any multiple booting between it and earlier versions such as DOS
or Windows 3.x.)
I fail to see where the Mac approach is any different, remember that with
Windows 95B, you can read any directly attached disk drives formatted under
FAT16 or FAT32. With Windows 95 A or Windows 95 or Windows 3.x or DOS, you
cannot read a directly attached disk drive formatted under FAT32. Neither
can you with Windows NT. You can, however, access any file system format
from any platform via a network with no problems. So, if you have a new
PCs with disk drives greater than 2GB, go ahead and install FAT32 (it
probably is on there already.) It is only for folks like myself who
dual-boot between NT and Windows 95 that this presents a problem. From how
Bruce explains, Macs will have the same problem. The old Macs cannot
access disks formatted under HFS-Plus. The new MacOS will let you access
HFS and HFS-Plus. Just like Windows 95B can access FAT16 and FAT32.
The big bugaboo is NTFS. But as Apple has nothing equivalent to it, so
there is no comparison to draw here.
There are a number of other reasons why one would put Windows 95B only on a
brand-new machine and they have nothing to do with the file system. Rather
they deal with bus-mastering cards, PCI-bridging, BIOS level and other
hardware issues. This is why Mickey$oft is only releasing OSR2 through
OEMs (hence its name) and the MSDN. There is a lot more to Windows 95B
than FAT32. We shall see what Apple does.
MPE/V had the 16 bit limitation. A file could only be as big as 32 extents
of 16 bits worth of 256byte sectors. 32 * 65,535 * 256 which amounted to
about a half GB of file size. The biggest disk drives during the reign of
MPE/V was the Eagle at 540MB. I cannot recall whether any bigger disk
drive was supported on MPE/V, perhaps the Coyote? But through the magic of
this list, we will soon find out. When MPE/XL was born, the biggest file
was 2^^31 bytes or 2.1 gigabytes. Later it was discovered that a negative
value in byte addressing was not likely to be encountered, so the limit was
raised to 2^^32 or 4 gigabytes.
Kind regards,
Denys. . .
Denys Beauchemin
Hicomp America, Inc.
[log in to unmask] www.hicomp.com/hicomp
(800) 323-8863 (281) 288-7438 fax: (281) 355-6879
-----Original Message-----
From: Bruce Toback [SMTP:[log in to unmask]]
Sent: Sunday, June 08, 1997 6:42 PM
To: [log in to unmask]
Subject: Re: URL naming
Alfredo writes:
>Are you saying that Windows 95 is just now going to a 32-bit file system?
>My Mac has been 32-bit clean since 1991 (or even before)... And MPE
since
>1987... Mmmm... Just wondering about the future, about which some
>people passively seem to have no choice :-)
"32 bit file system" in this context is a bit misleading. The FAT file
system, like the Mac's Hierarchical File System (HFS), uses a 16-bit
allocation block pointer. This limits the number of allocation blocks on
a volume to 65536. Since the minimum size of a file is one allocation
block, very large volumes have inefficient disc allocation (and
incidentally, a limit of something less than 65536 files per volume). For
example, a 4GB volume would have a minimum file size of 64KB (65536
allocation blocks of 65536 bytes each).
Win95's latest encarnation, which isn't available except if you buy a new
system or happen to belong to one or another of Microsoft's clubs, offers
a file system with 32-bit allocation block pointers. It's incompatible
with anything else in the Universe, including WinNT, so I can't use it,
but it's there. The larger allocation block pointers mean that you can
have more blocks per volume, so allocation block sizes can be a lot
smaller. (NTFS uses a completely disc format and doesn't have the
allocation block size problem. Win95 can't use NTFS volumes.)
Apple's solution is called HFS-Plus, and it should be available by the
end of the year. It will be compatible with HFS for small volumes (i.e.,
an old computer can mount a small HFS-Plus volume). They've also done
some magic so that programs that traverse the directory won't break
unless they actually do calculations with the allocation block pointer.
The software was demonstrated at the Worldwide Developer Conference last
month.
-- Bruce
--------------------------------------------------------------------------
Bruce Toback Tel: (602) 996-8601| My candle burns at both ends;
OPT, Inc. (800) 858-4507| It will not last the night;
11801 N. Tatum Blvd. Ste. 142 | But ah, my foes, and oh, my friends -
Phoenix AZ 85028 | It gives a lovely light.
[log in to unmask] | -- Edna St. Vincent Millay
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