1. CS-401 Computer Architecture & Assembly Language Programming
Lecture-31
Multitasking

2. Lets revise the last lecture

3. Multitasking/Multithreading

4. Thread Initialization
CS:IP = thread entry point
SS:SP = next free stack
Flags = 0x0200
AX,BX,CX,DX,SI,DI,BP,ES = don’t care
DS = depends upon registration mechanism

5. Thread Initialization
mov si,[nextpcb]
mov cl,9
shl si,cl
add si,256*2+stack
mov ax,[bp+4]
sub si,2
mov [si],ax

6. Thread Initialization
mov si,[nextpcb] 3
mov cl,9
shl si,cl
add si,256*2+stack
mov ax,[bp+4]
sub si,2
mov [si],ax

7. Thread Initialization
mov si,[nextpcb]
mov cl,9
shl si,cl
add si,256*2+stack
mov ax,[bp+4]
sub si,2
mov [si],ax

8. Thread Initialization
mov si,[nextpcb]
mov cl,9
shl si,cl
add si,256*2+stack
mov ax,[bp+4]
sub si,2
mov [si],ax SI SI

9. Thread Initialization
mov ax,[pcb+28]
mov [pcb+bx+28],ax
mov ax,[nextpcb]
mov [pcb+28],ax

10. Thread Initialization
mov ax,[pcb+28]
mov [pcb+bx+28],ax
mov ax,[nextpcb]
mov [pcb+28],ax
PCB 0
PCB 1

11. Thread Initialization
mov ax,[pcb+28]
mov [pcb+bx+28],ax
mov ax,[nextpcb]
mov [pcb+28],ax
PCB 0
PCB 1

12. Thread Initialization
mov ax,[pcb+28]
mov [pcb+bx+28],ax
mov ax,[nextpcb]
mov [pcb+28],ax
PCB 0
PCB 1

13. Thread Initialization
mov ax,[pcb+28]
mov [pcb+bx+28],ax
mov ax,[nextpcb]
mov [pcb+28],ax
PCB 0
PCB 1
PCB 2

14. Thread Initialization
mov ax,[pcb+28]
mov [pcb+bx+28],ax
mov ax,[nextpcb]
mov [pcb+28],ax
PCB 0
PCB 1
PCB 2

15. Thread Initialization
mov ax,[pcb+28]
mov [pcb+bx+28],ax
mov ax,[nextpcb]
mov [pcb+28],ax
PCB 0
PCB 1
PCB 2