>One other thing remains. Most PDP11s have what's called a 'line time
>clock' -- basically an interrupt every mains cycle. This is counted by
>the real time clock program in most OSes, and used to keep real time,
>etc. Of course if you move a machine from 60Hz to 50Hz power or vice
>versa, the real time clock will run slow/fast until you re-SYSGEN the OS
>for the appropriate frequency.
On many of the operating systems, you don't have to do a SYSGEN - just
tweak a number in the configuration word and viola, it's now a 50Hz machine.
For an RT-11 machine, in particular, you can tweak this on a running
system if you wish:
.type 50hz.mac
.MCALL .PVAL, .EXIT
; RMON Fixed offsets
CONFIG = 300 ;Configuration word 1
CLK50$ = 000040 ;50-cycle system clock
HZ50: .PVAL #AREA,#CONFIG,#CLK50$,BIS ;Get configuration word
.EXIT
AREA: .BLKW 4
.END HZ50
.macro 50hz
.link 50hz
.show conf
RT-11FB V05.07
Booted from DU1:RT11FB
USR is set SWAP
EXIT is set SWAP
KMON is set NOIND
MODE is set NOSJ
TT is set NOQUIET
ERROR is set ERROR
SL is set OFF
EDIT is set KED
FORTRAN is set FORTRA
KMON nesting depth is 3
CLI is set DCL, CCL, UCL, NO UCF
PDP 11/84 Processor
2048KB of memory
Floating Point Microcode
Extended Instruction Set (EIS)
Memory Management Unit
ECC Memory
Cache Memory
PMI Memory
60 Hertz System Clock
FPU support
.run 50hz
.show conf
RT-11FB V05.07
Booted from DU1:RT11FB
USR is set SWAP
EXIT is set SWAP
KMON is set NOIND
MODE is set NOSJ
TT is set NOQUIET
ERROR is set ERROR
SL is set OFF
EDIT is set KED
FORTRAN is set FORTRA
KMON nesting depth is 3
CLI is set DCL, CCL, UCL, NO UCF
PDP 11/84 Processor
2048KB of memory
Floating Point Microcode
Extended Instruction Set (EIS)
Memory Management Unit
ECC Memory
Cache Memory
PMI Memory
50 Hertz System Clock
FPU support
--
Tim Shoppa Email: shoppa_at_trailing-edge.com
Trailing Edge Technology WWW: http://www.trailing-edge.com/
7328 Bradley Blvd Voice: 301-767-5917
Bethesda, MD, USA 20817 Fax: 301-767-5927
Received on Sat Mar 25 2000 - 13:28:26 GMT