WebHASE: Tomasulo's Algorithm

Welcome to the WebHASE viewer applet for the HASE simulation of the Tomasulo's Algorithm. The applet may take some time to load

WebHASE creates two Java applet windows, one displaying the model and one containing the Playback Controls which can be used to start, stop, pause and rewind the animation. The animation shows what happens in the simulation model of Tomasulo's Algorithm as instructions and data from the Instruction/Data Source unit are processed. The contents of the Source unit can be viewed by activating the mouse over the Source unit icon and selecting the appropriate View option. Each option brings up a viewing window (note that the viewing windows may sometimes need to be resized).

Demonstration Program

Program instructions	Pseudo instructions
LOAD F0 0	LD F0 FLB1
LOAD F1 2	LD F1 FLB2
MULRS F1 3	MUL F1 FLB3
ADDRR F0 F1	ADD F0 F1
LOAD F2 4	LD F2 FLB4
MULRS F2 5	MUL F2 FLB5
ADDRR F0 F2	ADD F0 F2
LOAD F3 6	LD F3 FLB6
MULRS F3 7	MUL F3 FLB1
ADDRR F0 F3	ADD F0 F3
LOAD F1 8	LD F1 FLB2
MULRS F1 9	MUL F1 FLB3
ADDRR F0 F1	ADD F0 F1
STORE F0 1	ST F0 SDB1
STOP 0	STOP 0

Program Actions

LD F0 FLB1

• Sets FLB1 tag in FPR0; when the data arrives in FLB1 it is copied into FPR0

LD F1 FLB2

• Sets FLB2 tag in FPR1; before the data arrives, the tag has been moved to Multiply RS1 Source, so the data goes there instead

MUL F1 FLB3

• Uses Multiply Reservation Station 1
• Copies FLB2 tag from FPR1 to RS1 Sink and sets Multiply RS1 tag in FPR1
• Sets FLB3 tag in RS1 Source; when the data arrives in FLB3 it is copied into RS1 Source
• When result appears on CDB it is copied into FPR1 and Add RS1 Source

ADD F0 F1

• Uses Add Reservation Station 1
• Copies data from FPR0 to RS1 Sink and sets Add RS1 tag in FPR0
• Copies Multiply RS1 tag from FPR1 to RS1 Source
• When result appears on CDB it is copied into Add RS2 Sink

LD F2 FLB4

• Sets FLB4 tag in FPR2; before the data arrives in FLB4, the tag has been moved into Multiply RS2 Source so the data goes there instead

MUL F2 FLB5

• Uses Multiply Reservation Station 2
• Copies FLB4 tag from FPR2 to RS2 Sink and sets Multiply RS2 tag in FPR2
• Sets FLB5 tag in RS2 Source; when data arrives in FLB5 it is copied into Multiply RS2 Source
• When result appears on CDB it is copied into FPR2 and Add RS2 Source

ADD F0 F2

• Uses Add Reservation Station 2
• Copies Add RS1 tag from FPR0 to RS2 Source and sets Add RS2 tag in FPR0
• Copies Multiply RS2 tag from FPR2 to RS2 Sink
• When result appears on CDB it is copied into Add RS3 Sink

LD F3 FLB6

• Sets FLB6 tag in FPR3; as the data arrives in FLB6, the tag is being moved into Multiply RS2 Source so the data goes there instead

MUL F3 FLB1

• Uses Multiply Reservation Station 1
• Sets Multiply RS1 tag in FPR3
• Takes FLB6 tag from FPR3, but FLB6 tag and data appear on the CDB before the tag is sent to RS1 Sink, so the data is sent instead
• Sets FLB1 tag in RS1 Source
• When result appears it is copied into FPR3 and Add RS3 Source

ADD F0 F3

• Uses Add Reservation Station 3
• Copies Add RS1 tag from FPR0 to RS3 Sink and sets Add RS3 tag in FPR0
• Copies Multiply RS2 tag from FPR3 into RS3 Source
• When result appears it is copied into Add RS1 Sink

LD F1 FLB2

• Sets FLB2 tag in FPR1; when the data arrives it is copied into Multiply RS1 Source

MUL F1 FLB3

• Uses Multiply Reservation Station 2
• Takes Add RS3 tag from FPR1, but this tag appears on the CDB before the tag is sent to Multiply RS2 source, so data is sent instead
• Sets Multiply RS2 tag in FPR1
• Would set FLB3 tag in RS2 Source, but FLB3 tag and data appear on the CDB before the tag is sent to RS2, so data is sent instead
• When result appears it is copied into FPR1 and Add RS1 Source

ADD F0 F1

• Uses Add Reservation Station 1
• Copies Add RS3 tag from FPR0 to RS1 Sink and sets Add RS1 tag in FPR0
• Copies Multiply RS2 tag from FPR1 to RS1 Source
• When result appears it is copied into FPR0 and SDB1

ST F0 SDB1

• Copies Add RS1 tag from FPR0 into SDB1. When the data arrives it is sent to Memory