V1/man/man7/boot.7
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 reserved 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 location 54000 and transfers to 54000.
The other ROM program (address 173740) reads a DECtape
sitting in the end--zone on drive 0 into core location 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 *$5400Q 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) examines the
console switchs and executes one of several internal
programs depending on the setting. If no setting is
recognizable, bos loops waiting for a recognizable setting.
The following settings are currently recognized:
173700
73700 Will read Warm UNIX from the RF into core location
0 and transfer to 400.
11/3/71 BOOT PROCEDURES (VII)
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 signal 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
DECtape (blocks 1--32) and copies the data to the highest 16K
words of the RF. Thus this initializes 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 execution 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 (using /dev/rf0) onto blocks 1 thru
32. It has internally a list of files to be copied from
block 33 on. This list follows:
/etc/init
/bin/chmod
11/3/71 BOOT PROCEDURES (VII)
/bin/chown
/bin/cp
/bin/1n
/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 mandatory. /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, and msys are maintained offline
and must be reassembled before 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