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DISK.DOC
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1991-09-08
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DISK
All you wanted to know about your disks, but didn't know how to ask.
DISK provides information about your disk drives and disk controller. DISK
gives you information that would take several other utilities including DEBUG to
duplicate. DISK is for those times when you need to know something about the
physical characteristics of your drives as FDISK, DOS, and the BIOS understand
them.
Let's say you have carefully studied the choices and have decided which hard
disk to buy. Now you need to know whether your disk controller will support
that drive. DISK can help you determine what you have to do to install a new
drive and can give you the usage and formatting information on your current
drive.
You may discover that your controller is ready to support your new drive just by
changing the disk type through SETUP. If your controller doesn't directly
support your new drive, you will at least have enough information to use the
DSKSET and DSKDRV utilities to configure your controller for the new drive.
SHAREWARE
DISK and its related products BOOT, DSKSET, DSKDRV, DXTSET, and DXTDRV are
shareware. If you decide to use them after a reasonable trial period (1 month),
you are obligated to pay for them. The fee for continued use is $10. For this,
you may use the products indefinitely and I will send you notice of any updates
for one year. For $25, I will send you the source code immediately and will
send you any updates for one year. These fees apply to any use of the products
on a single computer including government agency and commercial use. Volume
discounts and site licenses are available to reduce the cost for large users.
Send the fees and any inquiries to:
Ronald Q. Smith
11 Black Oak Road
North Oaks, Mn. 55127-6204
You may also contact me via CompuServ mail at userid 71620,514. I will be
happy to respond to any problems and suggestions for future capabilities.
USING DISK
DISK displays information about both floppy and fixed disks and the fixed disk
controller. You may request information about either a logical drive (d:) or a
physical drive (0, 1, 0F).
DISK d[:]
d may be any drive letter including floppy drives, fixed drives, and virtual
drives. The allocation information associated with the drive is displayed as
shown in figure 1.
================================================================================
Figure 1. Disk Allocation Information
DISK Version 2.00 - Copyright 1989, 1991 Ronald Q. Smith
Information for drive C: volume label VOLUME_1 created Jul 18, 1989 10:48
DISK MEDIA MAXIMUM SECTORS/ HIDDEN RESRVED NUMBER SEC/ ROOT
TYPE DESCR CYLINDERS HEADS TRACK SECTORS SECTORS FATS FAT DIR
_____ _____ _________ _____ ________ _______ _______ ______ ____ ____
FIXED F8 923 5 17 17 1 2 77 512
TOTAL TOTAL SECTORS/ BYTES/ AVAILABLE AVAILABLE
BYTES CLUSTERS CLUSTER SECTOR BYTES CLUSTERS
_____________ __________ ________ ______ _____________ _________
33,462,272 16,339 4 512 4,812,800 2,350
================================================================================
DISK n[F]
n is a drive number and may be 0 or 1. If an F follows the number, information
about the floppy drive is displayed. The BIOS parameter table is displayed for
both fixed and floppy drives. The partition table (created by FDISK) is
displayed for fixed disks. If any of the partitions are extended DOS partitions
(partition type 5), the logical drive table for that partition is also dis-
played. See figure 2 for an example of the floppy disk display and figure 3 for
an example of a fixed disk display.
================================================================================
Figure 2. Floppy Disk Parameter Table
DISK Version 2.00 - Copyright 1989, 1991 Ronald Q. Smith
Information for floppy disk 0
SECT HEAD HEAD HEAD STEP MOTOR MOTOR
SIZE MAX LOAD SETTLE UNLOAD RATE NORMAL FORMAT FORMAT DATA START WAIT
BYTE SECT MS MS MS MS GAP GAP FILL LENGTH 1/8 S TICKS DMA
____ ____ ____ ______ ______ ____ ______ _____ _____ ____ _____ _____ ___
512 9 2 1 240 3 27 84 F6 255 8 37 YES
================================================================================
Figure 3. Fixed Disk Drive Information
DISK Version 2.00 - Copyright 1989, 1991 Ronald Q. Smith
Information for fixed disk 0
LAND REDUC WRITE TIMEOUT
TYPE CYL HD SEC ZONE WRITE PRECM ECC REC STD FMT CHK STP
____ ____ __ ___ ____ _____ _____ ___ ___ ___ ___ ___ ___
14 924 5 17 None 0 0 N/A YES N/A N/A N/A N/A
PARTITION TABLE
PART. PART. STARTING ENDING RELATIVE TOTAL
NO. TYPE BOOT CYL. HD SEC CYL. HD SEC SECTOR SECTORS
1 X-DOS NO 771 0 1 922 4 17 65,535 12,920
2 NONE NO 0 0 0 0 0 0 0 0
3 NONE NO 0 0 0 0 0 0 0 0
4 DOS16 YES 0 1 1 770 4 17 17 65,518
Press any key to see the logical device table for partition 1.
PARTITION 1 LOGICAL DEVICE TABLE
DEVICE PART. STARTING ENDING RELATIVE TOTAL
NO. TYPE BOOT CYL. HD SEC CYL. HD SEC SECTOR SECTORS
____ _____ ____ _____ __ ___ ____ __ ____ ______ ________
1 DOS12 NO 771 1 1 922 4 17 17 12,903
================================================================================
DISK TA[BLE]
The BIOS disk parameter table entries for all disk types supported by your
controller are displayed in edited form. See figure 4 for a sample display and
the section "The Format of the DISK Parameter Table" for a discussion of the
contents.
================================================================================
Figure 4. BIOS Fixed Disk Parameter Table
DISK Version 2.00 - Copyright 1989, 1991 Ronald Q. Smith
BIOS disk parameter table.
LAND REDUC WRITE TIMEOUT
TYPE CYL HD SEC ZONE WRITE PRECM ECC REC STD FMT CHK STP
____ ____ __ ___ ____ _____ _____ ___ ___ ___ ___ ___ ___
1 610 4 17 686 0 None N/A YES N/A N/A N/A N/A
2 615 4 17 615 0 300 N/A YES N/A N/A N/A N/A
3 615 6 17 615 0 300 N/A YES N/A N/A N/A N/A
4 960 5 17 None 0 512 N/A YES N/A N/A N/A N/A
5 920 9 17 None 0 None N/A YES N/A N/A N/A N/A
6 1,000 8 17 None 0 512 N/A YES N/A N/A N/A N/A
7 900 15 17 None 0 None N/A YES N/A N/A N/A N/A
8 960 5 17 None 0 None N/A YES N/A N/A N/A N/A
9 600 4 17 656 0 128 N/A YES N/A N/A N/A N/A
10 960 5 17 978 0 978 N/A YES N/A N/A N/A N/A
11 614 4 17 665 0 None N/A YES N/A N/A N/A N/A
12 1,000 5 17 None 0 512 N/A YES N/A N/A N/A N/A
13 600 4 17 665 0 None N/A YES N/A N/A N/A N/A
14 924 5 17 None 0 0 N/A YES N/A N/A N/A N/A
================================================================================
DISK TAX
The BIOS disk parameter table entries for all disk types supported by your
controller are displayed as 16 hex values. This information will help you
create your own entry using DSKSET and DSKDRV. See figure 5 for a sample
display.
================================================================================
Figure 5. Hex BIOS Fixed Disk Parameter Table
DISK Version 2.00 - Copyright 1989, 1991 Ronald Q. Smith
BIOS disk parameter table.
TYPE HEX
1 62 02 04 00 00 FF FF 00 00 00 00 00 AE 02 11 00
2 67 02 04 00 00 2C 01 00 00 00 00 00 67 02 11 00
3 67 02 06 00 00 2C 01 00 00 00 00 00 67 02 11 00
4 C0 03 05 00 00 00 02 00 00 00 00 00 00 00 11 00
5 98 03 09 00 00 FF FF 00 08 00 00 00 00 00 11 00
6 E8 03 08 00 00 00 02 00 00 00 00 00 00 00 11 00
7 84 03 0F 00 00 FF FF 00 08 00 00 00 00 00 11 00
8 C0 03 05 00 00 FF FF 00 00 00 00 00 00 00 11 00
9 58 02 04 00 00 80 00 00 00 00 00 00 90 02 11 00
10 C0 03 05 00 00 D2 03 00 00 00 00 00 D2 03 11 00
11 66 02 04 00 00 FF FF 00 00 00 00 00 99 02 11 00
12 E8 03 05 00 00 00 02 00 00 00 00 00 00 00 11 00
13 58 02 04 00 00 FF FF 00 00 00 00 00 99 02 11 00
14 9C 03 05 00 00 00 00 00 00 00 00 00 00 00 11 00
================================================================================
FDISK and CHKDSK display some of the same information as DISK, but FDISK makes
you walk through a series of menus. A display of the BIOS parameter tables is
not available with any of the common utilities. DISK may only be an interesting
addition to your set of utilities if you are not changing disk drives or working
with multiple systems. But, if you want to install a new drive or have to work
with PCs that you have not set up yourself, DISK can be invaluable.
THE FORMAT OF THE DISK PARAMETER TABLE
There are two disk parameter table formats, one for the PC/XT and one for the
PC/AT. Both require essentially the same information.
PC/AT
The PC/AT disk controller BIOS and parameter tables are located in the system
BIOS. The format of the PC/AT parameter table is:
BYTE SIZE DESCRIPTION
0 Word Total number of cylinders
2 Byte Number of read/write heads(surfaces)
3 Word Unused
5 Word Starting write precompensation cylinder
7 Byte Unused
8 Byte Control byte
Bit 7 No retry on disk errors
Bit 6 No retry on ECC errors
Bit 3 More than 8 heads
9 Byte Not used
10 Byte Not used
11 Byte Not used
12 Word Landing zone cylinder
14 Byte Sectors/track
15 Byte Reserved
Offset 0(word) - Contains the total number of cylinders. The drive specifica-
tions will supply this number. This number is 2 larger than the number that
will be returned to you when you make a request to retrieve drive parameters.
The innermost cylinder is reserved as a test cylinder and the returned drive
parameters give you the largest cylinder number (starting at 0) rather than the
number of cylinders.
Offset 2(byte) - Contains the total number of read/write heads. This is also
the number of read/write surfaces. Some disks have a clocking head/surface that
is not used for data and is not included in this count. The number in this
field is 1 greater than the number returned by a request to retrieve drive
parameters. Again, the returned drive parameters give the highest head number
(starting at 0) rather than the number of heads.
Offset 3(word) - Unused on a PC/AT. Set to 0.
Offset 5(word) - Starting write precompensation cylinder. Starting with this
cylinder, the controller applies modified logic for determining bit timing on
the disk surface. Each cylinder on the disk contains the same number of bits
but the inner (higher numbered) cylinders are substantially smaller than the
outer cylinders thus packing the bits closer together.
Offset 7(byte) - Unused on a PC/AT. Set to 0.
Offset 8(byte) - Control byte. Bit 3 is set to a 1 if your disk has more than 8
read/write heads. Bits 6 or 7 may be set if you have a special device driver
that does all its own device error recovery and does not want the controller to
attempt automatic recovery, but these bits are usually 0.
Offset 9(byte) - Unused on a PC/AT. Set to 0.
Offset 10(byte) - Unused on a PC/AT. Set to 0.
Offset 11(byte) - Unused on a PC/AT. Set to 0.
Offset 12(word) - Landing zone. Value to be used by park programs. Often equal
to the total cylinders value at offset 0, but some drives permit seeking to
higher cylinder numbers than can be used to contain data. The value may be zero
if the drive automatically retracts its heads at power off.
Offset 14(byte) - Sectors per track. Usually 17.
Offset 15(byte) - Reserved. Set to 0.
PC/XT
The PC/XT parameter table is located on the BIOS chip on the disk controller
card. This allowed the addition of optional controllers to a PC that was not
originally designed to accommodate them. Several of the fields are the same as
in the PC/AT parameter table. Those fields will be identified but not explained
again.
BYTE SIZE DESCRIPTION
0 Word Total number of cylinders
2 Byte Number of read/write heads(surfaces)
3 Word Reduced write current cylinder
5 Word Starting write precompensation cylinder
7 Byte Maximum ECC data burst length
8 Byte Control byte
Bit 7 No retry on disk errors
Bit 6 No retry on ECC errors
Bit 3 More than 8 heads
Bits 0-2 Step rate
9 Byte Timeout value for normal read/write operations
10 Byte Timeout value for format operations
11 Byte Timeout value for disk check operations
12 Word Unused
14 Byte Unused
15 Byte Reserved
Offset 0(word) - Normally all of the cylinder numbers are stored in Intel 80xxx
order with the low-order byte first. However, at least one XT controller stores
the values high-order byte first. Only the word fields (offsets 0, 3, 5, and
12) are affected. DISK attempts to compensate for this inversion in the edited
display. The hex display will always show the bytes in the order the controller
wants them. The hex display shows the bytes in the order they actually appear
in the table.
Offset 3(word) - Reduced write current cylinder. Because bits are packed more
closely on inner cylinders, it is often necessary to reduce the current used to
write the bits so that nearby bits are not effected (the bits are actually
smaller on the inner cylinders). The PC/AT controllers assume that this is the
same as the write precompensation cylinder and only use that value.
Offset 7(byte) - Maximum ECC data burst length. The maximum number of bits that
the ECC can correct. The first and last bits in error in any sector must be
within this length (inclusive) of each other or the ECC cannot correct the
error.
Offset 8(byte) - Control byte. Bits 0-2 specify the head step rate on cylinder-
to-cylinder motion.
Offsets 9-11(byte) - Timeout values. These values are used by the BIOS software
to timeout disk operations.
Offset 12(word) - Unused on a PC/XT.
Offset 14(byte) - Unused on a PC/XT.