hsc@mtuxo.UUCP (h.cohen) (06/28/86)
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.TL
Support of Larger Hard Disks and Two Hard Disks for Release 2 on PC 6300 PLUS
.AU
.AS 2
Various sizes of hard disks are supported on the PC 6300 PLUS. The sizes
range from 10MB to 68MB. Up to two disks can be installed on the system.
.P
This document describes the types of disks that are supported,
and their hardware and software setup.
Some restrictions on disk usage are also covered. Finally, some
suggestions on future enhancements are given.
.AE
.NS
All Members Department 6045413
M. Askinazi
C. Cirillo
H. S. Cohen
J. G. DeFelice
M. D. Jackson
D. Lindemulder
L. D. G. London
D. Ryan
A. Sparling ATT-IS Lisle, IL
S. A. Tartarone
.NE
.MT
.H 1 Introduction
Various sizes of hard disks are supported on the PC 6300 PLUS. The sizes
range from 10MB to 68MB. Up to two disks can be installed on the system.
.P
The following sections describe the types of disks that are supported,
and their hardware and software setup.
Some restrictions on disk usage are also covered. Finally, some
suggestions on future enhancements are given.
.H 1 "Disks Supported"
The PC 6300 PLUS in Release 2 will support only the disks listed in the ROM BIOS
(Basic Input-Output System).
There are eight entries in the latest BIOS, version 2.05, which contains
disk characteristics including the number of cylinders and heads.
.P
One can configure up to two hard disks and use any listed disk
for either drive. The first drive (drive 0) will be the only drive
from which the system will boot.
The second drive will be referred to as drive 1 throughout this document.
.P
Table 1 shows the disks that are listed in the BIOS table\*F.
.FS
Refer to Chapter 6 of Hardware Reference Manual for more detail.
.FE
.P
Note that entry 7 is the standard 20 MB disk used in the PC 6300 PLUS.
Even though disks of size 10 MB are supported, they are not recommended
for use as drive 0 since they are not big enough to install the UNIX system.
.P
Each track is assumed to have 17 sectors for all types of disks.
Different disk models may belong to the same BIOS table entry, for example,
entries 3 and 7, as shown in the table below, since they have the same
characteristics.
.DS 3
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Entry Size Mfgr Model Cylinders Heads
=
0 10MB Multi PC 6300 Type 306 4
_
1 30MB CDC Wren 697 5
_
2 20MB CMI CM6426 640 4
_
3 40MB Tandon TM755 981 5
40MB CDC Wren2-Slimline 981 5
_
4 40MB Seagate ST4051 977 5
_
5 68MB Miniscribe 6086 1024 8
_
6 68MB Micropolis 1325 1024 8
_
7 20MB Seagate ST225 612 4
20MB Miniscribe 3425 612 4
.TE
.DE
.TB "Disks Listed in BIOS"
.H 1 "DIP Switches Settings"
.P
To configure various hard disks either as drive 0 or drive 1 based on the
entries in the table, one needs to set switches on the motherboard and
and set jumper positions on the disk controller.
.P
On the motherboard, one needs to set switch 4 for drive 0 and switch 3 for
drive 1 on the switch labeled DSW-1. On the Disk Controller Board,
one needs to set jumper positions 3 and 4 for drive 0 and set positions 1 and 2 for
drive 1 on the switch labeled SW1\*(Rf.
.RS
Cohen, Harvey. Electronic Mail to Doris Ryan on DIP switches
.RF
.P
Table 2 shows the switch settings for hard disks of different
types and different drives.
.P
.B Closed
in the table means that a jumper should be installed
and
.B open
means that no jumper should be installed.
.P
A jumper needs to be installed on the disk itself.
The position of the jumper depends on the disk type and on the drive
selection (drive 0 or drive 1).
.P
The terminating resistor on the hard disk should be removed from the
first drive if a two-disk system is to be set up.
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Entry Motherboard Disk Controller Board
DSW-1 SW-1 Jumpers
=
4 (Drive 0) 4 (Drive 0) 3 (Drive 0)
3 (Drive 1) 2 (Drive 1) 1 (Drive 1)
=
0 on closed closed
_
1 on closed closed
_
2 on open closed
_
3 on open open
_
4 off closed closed
_
5 off closed open
_
6 off open closed
_
7 off open open
.TE
.DE
.TB "Switch Settings for Hard Disks"
.H 1 "Configurations Tested"
.P
Even though some disks combinations were not tested, it is expected that
they will work equally well since the disk driver, boot code, installation
procedure, and related commands
.RB ( fdisk
and
.BR format )
have been implemented to use the cylinder number and head number for calculation.
Appendix 1-1 contains a list of MRs that were fixed in Release 2
in support of various disk configurations.
.P
Also, the largest disk, 68MB, was tested to make sure there is no
boundary problem.
For example,
.B
fsck
.R
has been modified so that it can be compiled in large
model and therefore handle big file systems created on the larger disks.
Table 3 lists the configurations that have been tested.
.P
For the 40MB disks, we tested disks manufactured by Tandon and CDC only,
but not by Seagate.
.DS 3
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Drive 0 Drive 1
20MB 20MB
40MB 20MB
20MB 40MB
68MB None
20MB None
40MB None
.TE
.DE
.TB "Configurations Tested"
.H 1 "Tests Performed"
.P
Listed here are some preliminary tests done by the development group:
.AL a
.LI
Install UNIX system.
.LI
Run
.B
fdisk, format,
.R
and
.B
mkfs
.R
on the second drive.
.LI
Create files on second drive.
.LI
Issue reads and writes in an infinite loop for each drive. These two
loops are run simultaneously.
.LE
.H 1 Restrictions
.P
There are some restrictions when setting up hard disks that the user should
be aware of.
.AL a
.LI
A DOS partition cannot start at cylinder 0.
.P
For a DOS partition that starts at cylinder 0, the actual DOS file system
starts from sector 1 instead of sector 0. The UNIX disk driver assumes
all file system starts on a cylinder boundary. The sector offset is ignored
by the driver. This makes a DOS partition starting at cylinder 0
inaccessible under Simul-Task.
It is still accessible under pure DOS.
If the DOS partition is placed first on the disk, it should start at cylinder
1.
.LI
Only the DOS partition on the first drive, the E drive, is accessible under
Simul-Task.
.LI
If a DOS partition is moved after the UNIX system is installed, it will not be
accessible under Simul-Task.
.P
The UNIX system will have to be reinstalled and
the
.B format
step cannot be skipped in order for the DOS partition to be accessible
under Simul-Task.
.LI
A DOS partition should not extend beyond sector 65,536 (32MB).
.P
Each sector has 512 bytes.
This is a DOS limitation.
The last addressable cylinders for 40MB and 68MB disks are
771 and 481, respectively, if we convert sector 65,536 to the
corresponding cylinder number. On disks larger than 20MB, the DOS partition
must be placed first and the UNIX partition second.
.LI
Only one file system, the root file system, will be created on the first drive,
regardless of the disk size.
.P
The root file system is created automatically as part of the UNIX installation.
.LI
The user will have to create file systems on the second drive manually.
.P
Up to 4 file systems can be created on the second drive.
.LI
All administration of the second disk must be done though Bourne Shell
commands; there is no office interface.
.LI
The default partitioning of the boot disk will be
85/15 UNIX/DOS, regardless of the size of the disk.
.LI
The number of alternate tracks allocated (64) is the same for all size disks.
.LE
.H 1 "Software Set-Up of the Second Disk"\*F
.FS
This is documented in Chapter 8 of the Operations Guide.
.FE
.P
Since the first disk is set up as part of the UNIX installation, there is
very little the user will have to do except for partitioning the disk.
.P
For the second hard disk, the user needs to invoke the commands
.B fdisk
,
.B format
, and
.B mkfs
by hand and calculate the file system sizes by hand.
.P
The following are the steps to take for setting up the second hard disk:
.AL a
.LI
.B "/etc/fdisk /dev/rdsk/1s0"
.P
.B Fdisk
sets up the UNIX/DOS partition on the hard disk.
It is recommended that 100 percent of the disk be the UNIX partition,
since currently the DOS partition on the second drive is not accessible
under Simul-Task OS Merge. The UNIX partition should be set to "active".
.LI
.B "/etc/format /dev/rdsk/1s0 slice1 slice2 slice3 slice4"
.P
In order to specify the sizes of the optional slices,
you need to know how many sectors (in 512 bytes) there are available on your
active UNIX partition on your second hard disk.
The numbers used here for computing are 20MB disk specific. Refer to
Table 1 for the appropriate cylinder and head numbers.
.P
As mentioned earlier, there are 17 sectors (512 bytes per sector)
per track on all types of disk.
On a 20 MB disk, it has 4 tracks (heads) per cylinder, 68 sectors
per cylinder (17 X 4), and 612 cylinders per disk, providing
a total capacity of 41,616 sectors per disk.
.P
Since the first cylinder of a UNIX partition is reserved for storing
the boot code, bad track table and VTOC (Volume Table of Contents)
it is not available to the user. At least another 64 tracks should be
reserved as alternate tracks for bad track handling (which is equal
to 16 cylinders).
If a user uses 100% of the disk as the active UNIX partition, there will be 595
cylinders (612 - 17) left (which is equal to 40,460 sectors).
.P
Therefore, reserve 17, 14, 14, and 9 cylinders for disks of 20MB,
30MB, 40MB, 68MB respectively.
.P
After having calculated the space available, up to 4 slices can be defined
and used for raw disk space or file systems.
At least one slice should be specified to create a slice that uses all
the space available.
This is done by running the command
.B
format.
.R
The unit for these slices is 512-bytes.
The corresponding device node for these slices are /dev/[r]dsk/1s1 to
/dev/[r]dsk/1s4. These slices will be physically contiguous disk
areas, and the size specified will be rounded down to the nearest cylinder
boundary for efficiency reasons. Therefore, it is recommended
to use a multiple of the cylinder size.
.P
For example, to create one big slice:
.nf
/etc/format /dev/rdsk/1s0 40460
.fi
If a user has 40,460 sectors available and wants to create 4
slices, the user might do the following:
.nf
/etc/format /dev/rdsk/1s0 13600 6800 10200 9860
.fi
Note that each slice is a multiple of the cylinder size.
.P
In other words, a user has the freedom to specify the slice sizes
for the number of sectors available. No space (zero sector) will
be allocated for the unspecified slices. In the first example above,
the first slice (1s1) occupies 40,460 sectors and slices 2 to 4 have zero
length.
.P
.LI
.B "/etc/mkfs /dev/rdsk/1s[1-4] nnn"
.P
A file system can be created for each slice created.
Examples:
.nf
/etc/mkfs /dev/rdsk/1s1 40460 2 68
/etc/mkfs /dev/rdsk/1s1 13600 2 68
/etc/mkfs /dev/rdsk/1s2 6800 2 68
.fi
.LE
.H 1 "Suggestions for Future Enhancements to a Larger/Second Disk"
.AL a
.LI
Set up the second hard disk as part of the hardware setup under
office.
.LI
Make a DOS partition which starts at cylinder 0 usable under Simul-Task.
.LI
Make a DOS partition on the second disk accessible under Simul-Task.
.LI
Be able to create more than one file system for the first hard disk.
.P
It is desirable to be able to make more than one file system
when a larger disk (>40MB) is used as the first disk.
.LI
Be able to support other types of disks that are not in the current
BIOS table.
.LE
.H 1 "Conclusion"
While the system will support various types of disks and two disks,
there is still room for more functionality and flexibility as described
in this document.
.H 1 "Acknowledgements"
Doris Ryan provided much valuable input in writing this document.
Dave Lindemulder provided me much information on the hardware setup.
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.aH "Appendix 1: MR List"
.ce 1
MR LIST
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MR CP SB ABSTRACT
=
bl85-20717 cmd-s5 format L7 The default slice sizes are obsolete
_
uk86-00601 kern-s5 boot Larger hard disk support
_
bl86-02430 cmd-s5 format T{
In load "almost C2" format
has a problem formatting a 40M with bad tracks
T}
_
bl86-03143 kern-s5 boot T{
In load C2 on a 40MB hard disk,
problems booting
T}
_
bl86-03072 kern-s5 wini T{
Need to resend the disk drive
parameter for drive 0 when mounting the 2nd drive.
T}
_
bl86-03564 kern-s5 wini T{
Running "fdisk" on the second
drive under "lmgr" will wipe out the partition
T}
_
bl86-05627 cmd-s5 fsck T{
Fsck needs changing to handle
larger root file system
T}
_
bl86-05761 cmd-s5 fdisk T{
In load C3, default settings are
incorrect for 68M drive
T}
_
bl86-05762 cmd-s5 fdisk T{
In load C3, the format of partition
table is off with a 68M drive
T}
_
uk86-05605 kern-s5 wini T{
Wini driver sometimes timeout when
using second drive
T}
.TE