Mail Archives: opendos/1997/05/15/22:57:52
> That's why 32-bit disk access improves things an amazing amount under
> Windows 3.11 and a SCSI drive, and doesn't do much at all for an old
> IDE.
Let's see if I can explain about "32-bit disk access".
DOS uses BIOS routines to access the display, keyboard, hard disk,
diskette, COM port and printer.
Say a program wants to read a file from the hard disk. It asks the
BIOS to get the information. The BIOS sends the request to the disk
adapter then waits for the information to come back. "Is it
there yet? No. Is it there yet? No." After some delay the information
finally arrives and the system goes back to doing useful work.
If you're a single user doing word processing, this doesn't matter. If
you're on a network with 20 other users, then it's a big problem. It
means that the entire system stops every time you read a file.
This is why servers can't use DOS and BIOS to access the hard disk.
Novell made its money with Netware by offering a multi-tasking,
BIOS-avoiding operating system when Microsoft and IBM only had
DOS-based servers.
The evolution of Windows has been to eliminate BIOS one step at a
time. Windows 3.1 already used its own devices rather than DOS services
to access the display, the mouse and the keyboard.
The next step was for Windows to access the hard disk itself. This was
done with Windows for Workgroups 3.11. With 32-bit disk access, Windows
manipulates the hard disk directly, without using BIOS.
Note the name "Windows for Workgroups": the difference between Windows
3.1 and WfWG 3.11 is that WfWG no longer uses BIOS to access the hard
disk, but this single difference means that Windows for the first time
becomes suitable for workgroups and networks.
(As it happens, WfWG 3.11 only has 32-bit disk access for IDE disks.
SCSI disk support had to wait until Windows 95.)
So the deal with 32-bit disk access isn't really that you can read
data twice as fast if you read it 32 bits at a time rather than 16
bits at a time. Rather, the significance is that you're no longer
using BIOS and stopping the entire system every time you read
something on a disk. A single user might not see a big difference, but
it's crucial on a multi-user system.
So once again "32-bit" is generally better than "16-bit", but not as
much as the hype implies, and perhaps not enough to matter to the
average user.
Regards,
--
Yves Bellefeuille See homepage for best freeware for DOS and Win 3.1x
Ottawa, Canada Finger, homepage or key-server for PGP key
an448 AT freenet DOT carleton DOT ca Francais / English / Esperanto
http://www.ncf.carleton.ca/~an448/
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