jph@cbdkc1.UUCP (J. P. Holtman #3B370 CB x2214 JPH) (10/24/86)
There was a posting a while back on how to modify the boot sector on the hard disk so that the cluster size was 2K instead of the default 8K. Now that I have a 6300+ I am in need of that patch. Can someone forward it to me. Thanks
gpw@ihdev.UUCP (G. P. Wilkin) (10/25/86)
> There was a posting a while back on how to modify the boot sector on > the hard disk so that the cluster size was 2K instead of the default > 8K. Now that I have a 6300+ I am in need of that patch. Can someone > forward it to me. > > Thanks Here's the clear story (published internally in the 6300 Newsletter , so why don't you take a look? :-) ) 1) You don't need to do ANYTHING special, IF you have a 20 meg drive. Just get yourself a LEGAL copy of PC-DOS 3.1 or 3.2, then: 2) Back up you hard disk, completely. 3) Reformat your hard disk using the pc dos 'format' command (a:format/s c:) 4) Copy the pc-dos version of command.com to the hard disk along with the majority of the pc-dos tools. 5) Copy the AT&T versions of BASIC, BASICA, and GWBASIC to your hard disk/ 6) get a copy of the program AT&T_CLK to set the clock properly. (It's on some BBS, I don't have the numbers here now) 7) Restore the files you backed up (don't change the dos directory) All bets off for 10meg drives. NOT tested with the SIMULTASK - OS MERGE Option. IF you have to low level format, follow the instructions given with the disk. (if you don't have instructions, call for help. DON'T Guess, Don't use suggestions. The AT&T 6300 Plus Requires a specific sequence if you use Simultask-OS Merge) This is just off the top of my head at 10:00pm on a friday night, so wait till I post the complete story in a day or two if you have ANY doubts. gpwilkin -- George Wilkin AT&T Network Systems, Naperville, IL !ihnp4!ihdev!gpw IH 4A-157 work 312-979-4317
harrison@ucsfcgl.UUCP (Peter Harrison%MIS) (10/29/86)
I used this on my Compaq and it worked with a little fiddling. Compaq
kept rewriting the boot sector fixing all the changes. I finished up
using the IBM versions of the two hidden system files for the BIOS,
doing all the changes and then finished up by copying in the Compaq
COMMAND.COM.
Your question indicated a default 8k cluster size. DOS 3.n should
default to a 4k cluster size on a 10 meg disk. On anything over 16 meg
it should defa`ult to a 16 bit FAT and a 2k cluster size, so unless you
have something wierd, this may not work.
Enjoy
Peter Harrison
UUCP: ucbvax!ucsfcgl!harrison
ARPA: harrison@ucsf.cgl.edu
Phone: (415) 355-2149
US Mail: 419 Roberts Rd., Pacifica, CA 94044-3246
-------------- forwarded text begins --------------
From: brown@nicmad.UUCP
Newsgroups: net.micro.pc
Subject: DOS 3.10 patches, update
Message-ID: <341@nicmad.UUCP>
Date: 4 Sep 85 22:22:10 GMT
Organization: Nicolet Instrument Corp. Madison WI
I guess that it comes in handy, running an IBM-PC BBS. That way I can get some
things from there and pass them on to here. Anyway, a little while ago I put up
a couple of things to do with DOS3.10 patches. Well, it has been put together
in one text file. So, I am posting it to the net.
The upgrade/change to the FAT table to make 10MB hard disks use 2K cluster
sectors does indeed work. I have it on both of the 10MB drives that I am using.
I do suggest that a tape backup system is used or it will take a lot longer to
do this upgrade. The upgrade is fast and painless, but doing a floppy backup
and restore is not.
The CompuServe IBMPC SIG Users Group
------------------------------------
PATCHES FOR IBM DOS 3.1
-----------------------
************************************************************************
Note: In the patches which follow, it is assumed the user is familiar
with the use of DEBUG. The notation "xxxx" means "anything is ok".
The notation <cr> means press Enter.
************************************************************************
FIXED DISK CLUSTER SIZE
If you have a 10 Meg hard disk, the following information collated by
Bill Higgins, provides for 2K clusters instead of the standard 4K
clusters. Typically, you will free up about 10% of the disk space you
are currently using.
2K Cluster Size for 10MB Fixed Disks under DOS 3.1
Standard 10mb fixed disks formatted under DOS 3.1 utilize 4k clusters
(i.e., the minimum space allocated to any file is 4096 bytes), while
drives 20mb and larger utilize 2k clusters. I use a PC with twin 10mb
drives under DOS 3.1. Since I have a multitude of small files on these
disks, the smaller allocation unit's space saving advantage far outweighs
any theoretical disadvantage of additional overhead for DOS to handle the
added allocation units.
With the help of Bob Morse, SysOps Jim Gainsley, and Conrad Kageyama,
and the DOS Technical Reference, I was able to make the changes necessary
to use 2k clusters on both of my 10mb drives. By following the
step-by-step instructions below, you will be able to make the switch to
2k clusters yourself.
NOTE: THE FOLLOWING PROCEDURE WILL DESTROY ALL DATA ON THE FIXED DISK!!!
You will need the following:
(1) IBM PC-DOS version 3.1 (3.0 appears NOT to work).
(2) A disk utility such as DISK REPAIR (a part of the IBM PROFESSIONAL
DEBUG FACILITY), or DISMOD (a USS program, available on many BBS's),
or equivalent. Note: You will not need this, if you use the
Alternate Method in #4a below.
Most critical to the process is the sequence in which this procedure is
attempted. Here is the 4k to 2k cluster procedure:
(1) Do a complete backup of the fixed disk, using your current version
of DOS.
(2) Cold boot DOS 3.1, run FDISK to create or be sure that a DOS
partition exists on the Fixed Disk.
(3) Format the fixed disk using the DOS 3.1 FORMAT.COM program. Do NOT
use any parameters (no /s or /v).
(4) Using your disk utility, select the boot sector and view it.
See below for an explanation of the pertinent info in this sector.
At location AA below, you should see a value of 08 which is the
number of sectors per cluster. Change this to 04.
At location BB below, you should see a value of 0800 which is the
number of sectors per fat (in hex Word format). Change this to 1500.
The results should appear as in CC and DD below.
All changes to the fat sectors required for 2k clusters will be
accomplished by the subsequent format in instruction 6 below. No
other manual changes are required.
--------------------
Example of first few bytes in the Boot Sector of the fixed disk,
displayed in hex format, after formatting with DOS 3.1, and prior
to 2k cluster size changes: (The bytes of interest are located at
Boot sector Offsets 0Dh = Sectors per cluster, and 16h = Sectors
per FAT.)
EB299049 424D2020 332E3100 02080100 020002F3 50F80800
^^ ^^^^
AA BB
After the 2k cluster size changes:
EB299049 424D2020 332E3100 02040100 020002F3 50F81500
^^ ^^^^
CC DD
Where the data elements directly above AA are sectors per cluster,
and above BB are sectors per FAT.
(4a) Alternate Method:
If you would rather, and if you are familiar with the operation
of Debug, the following method can be used.
Under DOS 3.1, do:
DEBUG
-L 0 n 0 1 <cr>
-E 0D <cr>
xxxx:0D 08.04 <cr>
-E 16 <cr>
xxxx:16 08.15 <cr>
-W 0 n 0 1 <cr>
-Q
where, n = the fixed disk drive as follows:
If fixed disk is drive B then n=1
" C " n=2
" D " n=3
" E " n=4
NOTE: Be *really* careful when you do the L and W commands in
the foregoing sequence. Would be best to check your
work by doing DEBUG, then
-L 0 n 0 1 <cr> then doing
-D 0D L1 <cr> and
-D 16 L1 <cr> making sure that the results
are 04 & 15 respectively.
Then exit by doing
-Q
-------------------
A more detailed explanation of these two changes:
The number of sectors per cluster would change from 08 to 04, since
that's what this is all about. The sectors per FAT will change, in
order to accomodate (1) the increased number of possible FAT
entries, and (2) the increased size of each fat entry which will be
in 16-bit format instead of the former 12-bits. The value to use for
a 10 meg & 2k clusters would be 21 sectors, or 1500 in hex word
format. (In this case the 15 is all that counts. 15 hex = 21 decimal.)
(5) Exit the disk utility and do a cold boot with DOS 3.1. This is
critical, since the boot sector is read by DOS only once, at boot
time, in order to build the BIOS Parameter Block. Having different
info in the boot sector than what's in the memory-resident BPB will
give UNPREDICTABLE RESULTS.
The following is safest way to preceed. Please use it.
(6) Reformat the drive using the DOS 3.1 FORMAT.COM,
FORMAT C: /S
(You may also include /V, if you wish to include a volume label.)
DOS 3.1 FORMAT will NOT affect your changes to the boot
sector. (This a change from DOS 3.0 FORMAT, which re-writes
the boot sector.)
(7) Restore your files, BEING SURE TO USE the RESTORE parameter, /P
which prompts before restoring system files.
**** WARNING ****
YOU MUST NOT ALLOW THE TWO SYSTEM FILES, IBMBIO.COM AND IBMDOS.COM
TO BE RESTORED, EVEN IF THEY ARE DOS 3.1 !!! IF YOU DO, THEY WILL
NOT BE PUT IN THE PROPER LOCATIONS AND YOUR FIXED DISK WILL NOT BE
BOOTABLE AND YOU WILL HAVE TO REFORMAT !!!
Avoid restoring an earlier version of COMMAND.COM, but if you do
restore an earlier version, nothing is lost, just be sure to copy
a 3.1 version over it afterwards. You should now be operational
again, with 2k clusters.
Further info on the entries in the boot sector entries used to build
the BIOS Parameter Block can be found in the DOS 3.1 Technical
Reference, Page 2-28. Of course, I cannot warrant that this change
will work for all controller/disk combinations, particularly for
controllers and drives which are not 'XT clones' though it 'should
work' for all drives compatible enough to work under DOS 3.1.
Comments to: -- Bill Higgins [70575,307] CIS, IBMPC SIG --