35. Hardware Problems
• Different user programs (and supervisor) may interfere
with each other
• Input-output equipement may be initiated by a user and
read words in on another user program
• Time sharing supervisor must be able to interrupt user
program after a quantum of computation
• Large core memories (e.g.. a million words) would ease
the system programming complications immensely
since the different active user programs, systems
programs could remain in core memory at all times.
36. Hardware Problems
• Different user programs (and supervisor) may interfere
Memory Protection
with each other
• Input-output equipement may be initiated by a user and
Trap all input-output
read words in on another user program instructions
• Time sharing supervisor must be able to interrupt user
Time controlled
program after a quantum of computation interrupt
• Large core memories (e.g.. a million words) would ease
the system programming complications immensely
8 MB RAM ;-)
since the different active user programs, systems
programs could remain in core memory at all times.
37. Programming Problems
• Supervisor should charge user usage
accounting automatically
• Supervisor should coordinate all user
input-output
• Good system programs tooling
38. Usage Problems
• Too large a computation or excessive
typewriter output may be requested
• Since real time is not usage-time,
supervisor must inform user
• Computer malfuntions must be expected
39. 7094 Modifications
• Standard 60 cycle accounting and interrupt
clock
• Memory boundary and relocation register
• 2 32,768 Core memory bank for the
nd
supervisor
• 7094 has become a two-mode machine
40. Supervisor
• Provided virtual machines
• 3 foreground machines which run 7094
instructions and could invoke supervisor
services
• 1 background machine with tape access
• Scheduling
• Managed I/O
41. Memory protection
• 32k memory is managed in 128 blocks of 256
words
• 3 7 Bit registers
5 7 5
base end relo
• Protection check
base [ 5* 256 ]<= addr <= end [ 7 * 256 ]
42. Instruction protection
• User mode: subset of 7094 instructions
• Memory access only to defined region by
memory relocation and protection
• Certain instructions are forbidden and invoke
protection trap
43. Instruction protection
Privileged
instructions
• all
I/O
instructions
(RDS,
WRS,
BSR,
BSF,
User mode: subset of 7094 instructions
• Memory access only
SDN,
RUN,
REW,
etc)
to defined region by
memory relocation and protection
all
channel
instructions
(RCHx,
LCHx,
SCHx,
• Certain instructions are forbidden and invoke
etc)
protection trap
all
I/O
transfer
instructions
(TEFx,
TRCx,
TCOx,
TCNx)
plus
and
minus
sense
(+0760...
and
-‐0760...)
45. Multi Level Feedback Queue
• Task is put into level l0
dependent on its actual size (calculation time)
• Execution time in level x is 2x quanta
• If task is not completed, it is put at the end of
level x+1 queue
• MLFQ is preemptive
54. TYPSET & RUNOFF
• TYPSET for creating and editing files
• High speed input mode
• Edit mode
• RUNOFF
• Control words in the text
• Line-length, indention, alignment
55. MAIL
• Described in Programming Staff Note 39
• Created file MAIL BOX in directory
• User has been informed about new mail
56. MAIL
• Described in Programming Staff Note 39
• Created file MAIL BOX in directory
• User has been informed about new mail
57. MAIL
• Described in Programming Staff Note 39
• Created file MAIL BOX in directory
• User has been informed about new mail
58. MAIL
• Described in Programming Staff Note 39
• Created file MAIL BOX in directory
• User has been informed about new mail
59. RUNCOM
• File-system file of commands to be
executed in a batch
• Commands are usable like library
subroutine
61. Quellen
• REMINISCENCES ON THE HISTORY OF TIME SHARING
• Fernando J. Corbato, Marjorie Merwin Daggett, Robert C. Daley AN EXPERIMENTAL
TIME-SHARING SYSTEM, Proceedings of Spring Joint Computer Conference, May 3, 1962
• R.M. Fano, The MAC system: a progress report, MAC-TR-12
• http://www.ibiblio.org/apollo/Documents/CTSS_ProgrammersGuide.pdf
• http://www.multicians.org/thvv/7094.html
• http://www.multicians.org/thvv/mail-details.html
• http://www.frobenius.com/7090.htm
• http://motherboard.vice.com/2011/2/17/watson-s-hardest-question-what-is-life--2
• http://u-tx.net/media/fano-on-ctss.png
• http://mason.gmu.edu/~tbell5/page2.html
• http://www-03.ibm.com/ibm/history/exhibits/storage/storage_1301.html
• http://www-03.ibm.com/ibm/history/exhibits/mainframe/mainframe_PP7090.html
• http://simh.trailing-edge.com/docs/ctss_hardware.pdf
• http://mit.edu/saltzer/www/publications/ctss/CC-244.html
• http://en.wikipedia.org/wiki/Daisy_Bell
Simulator
• http://www.cozx.com/~dpitts/ibm7090.html
Videos
• http://www.youtube.com/watch?v=Q07PhW5sCEk
• http://www.youtube.com/watch?v=8edfFH0rklc