3/15/72 BOOT PROCEDURES (VII)
NAME bos, maki, rom, vcboot, msys, et al
SYNOPSIS --
DESCRIPTION On the RF disk, the highest 16K words are re-
served for stand-alone programs. These 16K words
are allocated as follows:
bos (1K)
Warm UNIX (7K)
Cold UNIX (8K)
The UNIX read only memory (ROM) is home cut with
2 programs of 16 words each. The first (address
173000) reads bos from the RF disk into core lo-
cation 154000 and transfers to 154000. The other
ROM program (address 173040) reads a DECtape sit-
ting in the end-zone on drive 0 into core loca-
tion 0 and transfers to 0. This latter operation
is compatible with part of DEC's standard ROM.
The disassembled code for the UNIX ROM follows:
173000: mov $177472,r0 12700;177472
mov $3,-(r0) 12740;3
mov $140000,-(r0) 12740;140000
mov $154000,-(r0) 12740;154000
mov $-2000,-(r0) 12740;176000
mov $5,-(r0) 12740;5
tstb (r0) 105710
bge .-2 2376
jmp *$154000 137;154000
173040: mov $177350,r0 12700;177350
clr -(r0) 5040
mov r0,-(r0) 10040
mov $3,-(r0) 12740;3
tstb (r0) 105710
bge .-2 2376
tst *$177350 5737;177350
bne . 1377
movb $5,(r0) 112710;5
tstb (r0) 105710
bge .-2 2376
clr pc 5007
The program bos (Bootstrap Operating System) ex-
amines the console switchs and executes one of
several internal programs depending on the set-
ting. The following settings are currently rec-
ognized:
??? Will read Warm UNIX from the RF into core
location 0 and transfer to 600.
1 Will read Cold UNIX from the RF into core
location 0 and transfer to 600.
10 Will dump all of memory from core loca-
tion 0 onto DECtape drive 7 and then
halt.
20 Will read 256 words from RK0 into core 0
and transfer to zero. This is the proce-
dure to boot DOS from an RK.
40 This is the same as 10 above, but instead
of halting, UNIX warm is loaded.
0 Will load a standard UNIX binary paper
tape into core location 0 and transfer to
0.
77500 Will load the standard DEC absolute and
binary loaders and transfer to 77500.
Thus we come to the UNIX warm boot procedure: put
173000 into the switches, push load address and
then push start. The alternate switch setting of
173030 that will load warm UNIX is used as a sig-
nal to bring up a single user system for special
purposes. See init(VII). For systems without a
rom, UNIX (both warm and cold) have a copy of the
disk boot program at location 602. This is prob-
ably a better warm boot procedure because the
program at 602 also attempts to complete out-
standing I/O.
Cold boots can be accomplished with the Cold UNIX
program, but they're not. Thus the Cold UNIX
slot on the RF may have any program desired.
This slot is, however, used during a cold boot.
Mount the UNIX INIT DECtape on drive 0 positioned
in the end-zone. Put 173040 into the switches.
Push load address. Put 1 into the switches.
Push start. This reads a program called vcboot
from the tape into core location 0 and transfers
to it. vcboot then reads 16K words from the DEC-
tape (blocks 1-32) and copies the data to the
highest 16K words of the RF. Thus this initial-
izes the read-only part of the RF. vcboot then
reads in bos and executes it. bos then reads in
Cold UNIX and executes that. Cold UNIX halts for
a last chance before it completely initializes
the RF file system. Push continue, and Cold UNIX
will initialize the RF. It then sets into execu-
tion a user program that reads the DECtape for
initialization files starting from block 33.
When this is done, the program executes /etc/init
which should have been on the tape.
The INIT tape is made by the program maki running
under UNIX. maki writes vcboot on block 0 of
/dev/tap7. It then copies the RF 16K words (us-
ing /dev/rf0) onto blocks 1 thru 32. It has in-
ternally a list of files to be copied from block
33 on. This list follows:
/etc/init
/bin/chmod
/bin/date
/bin/login
/bin/ls
/bin/mkdir
/etc/mount
/bin/sh
/bin/tap
Thus this is the set of programs available after
a cold boot. init and sh are mandatory. For
multi-user UNIX, getty and login are also neces-
sary. mkdir is necessary due to a bug in tap.
tap and mount are useful to bring in new files.
As soon as possible, date should be done. That
leaves ls and chmod as frosting.
The last link in this incestuous daisy chain is
the program msys.
msys char file
will copy the file file onto the RF read only
slot specified by the characacter char. Char is
taken from the following set:
b bos
u Warm UNIX
1 Cold UNIX
Due to their rarity of use, maki and msys are
maintained off line and must be reassembled be-
fore used.
FILES /dev/rf0, /dev/tap?
SEE ALSO init(VII), tap(I), sh(I), mkdir(I)
DIAGNOSTICS --
BUGS This section is very configuration dependent.
Thus, it does not describe the boot procedure for
any one machine.
OWNER ken