11/3/71 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 (6K)
Cold UNIX (6K)
unassigned (3K)
The UNIX read only memory (ROM) is home cut with
2 programs of 16 words each. The first (address
173700) reads bos from the RF disk into core lo-
cation 54000 and transfers to 54000. The other
ROM program (address 173740) 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:
173700: mov $177472,r0 12700;177472
mov $3,-(r0) 12740;3
mov $140000,-(r0) 12740;140000
mov $54000,-(r0) 12740;54000
mov $-2000,-(r0) 12740;176000
mov $5,-(r0) 12740;5
tstb (r0) 105710
bge .-2 2376
jmp *$54000 137;54000
173740: 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. If no setting is recognizable, bos loops
waiting for a recognizable setting. The follow-
ing settings are currently recognized:
173700
73700 Will read Warm UNIX from the RF into core
location 0 and transfer to 400.
1 Will read Cold UNIX from the RF into core
location 0 and transfer to 400.
2 Will read the unassigned 3K program into
core location 0 and transfer to 400.
10 Will dump 12K words of memory from core
location 0 onto DECtape drive 7.
0 Will load a standard UNIX binary paper
tape into core location 0 and transfer to
0.
57500 Will load the standard DEC absolute and
binary loaders and transfer to 57500.
Thus we come to the UNIX warm boot procedure: put
173700 into the switches, push load address and
then push start. The alternate switch setting of
73700 that will load warm UNIX is used as a sig-
nal to bring up a single user system for special
purposes. See /etc/init.
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 173740 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/chown
/bin/cp
/bin/ln
/bin/ls
/bin/mkdir
/bin/mv
/bin/rm
/bin/rmdir
/bin/sh
/bin/stat
/bin/tap
Thus this is the set of programs available after
a cold boot. /etc/init and /bin/sh are manda-
tory. /bin/tap and /bin/mkdir are used to load
up the file system. The rest of the programs are
frosting. As soon as possible, an sdate should
be done.
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
2 unassigned
Due to their rarity of use, maki and msys are
maintained off line and must be reassembled be-
fore used.
FILES /dev/rf0, /dev/tapn
SEE ALSO /etc/init, /bin/tap, /bin/sh, /bin/mkdir, bppt
format
DIAGNOSTICS --
BUGS The files /bin/mount, /bin/sdate, and /bin/date
should be included in the initialization list of
maki.
OWNER ken