浙江省深化普通高中课程改革方案.doc

Processes
Process – a program in execution; process execution must progress in sequential fashion
Textbook uses the terms job and process almost interchangeably
As a process executes, its state changes:
new: The process is being created
running: Instructions are being executed
waiting: The process is waiting for some event to occur
ready: The process is waiting to be assigned to a process
terminated: The process has finished execution
Diagram of Process State
As a process executes, it changes state
new: The process is being created
ready: The process is waiting to run
running: Instructions are being executed
waiting: Process waiting for some event to occur
terminated: The process has finished execution
Fetch
Exec
R0
…
R31
F0
…
F30
PC
…
Data1
Data0
Inst237
Inst236
…
Inst5
Inst4
Inst3
Inst2Inst1
Inst0
Addr 0
Addr 232-1
What happens during execution?
Execution sequence:
Fetch Instruction at PC
Decode
Execute (possibly using registers)
Write results to registers/mem
PC = Next Instruction(PC)
Repeat
PC
PC
PC
PC
CPU3
CPU2
CPU1
Shared Memory
Assume a single processor. How do we provide the illusion of multiple processors?
Multiplex in time!
Each virtual “CPU” needs a structure to hold:
Program Counter (PC), Stack Pointer (SP)
Registers (Integer, Floating point, others…?)
How switch from one CPU to the next?
Save PC, SP, and registers in current state block
Load