2. Function Unit Status FU Busy Op Dest Sop1 Sop2 Unit1Unit2 Rdy1 Rdy2 1[i] N 2[*1] Y Mult F0 F2 F4 No Yes 3[*2] N 4[+] Y Add F6 F8 F2 5[/] Y Div F10 F0 F6 2[*1] No Yes Registers:F0 F2 F4 F6 F8 F10 FU# 2[*1] 4[+] 5[/] 3.R egister R esultStatus The ADDF is Next to Complete. The changes are noted in Red. 1.Instruction S tatus Q ueue Instruction Issued O p R ead Ex C m pl Result LF F6,34(R2) X X X X LF F2,45(R3) X X X X M U LTF F0,F2,F4 X X SUBF F8,F6,F2 X X X X D IVF F10,F0,F6 X ADDF F6,F8,F2 X X X Question ADDF will try to write back. Why can it not do this now? * *
2. Function Unit Status
Jan 21, 2016
*. *. The ADDF is Next to Complete. The changes are noted in Red. Question ADDF will try to write back. Why can it not do this now?. 2. Function Unit Status. FU. Busy. Op. Dest. Sop1. Sop2. Unit1. Unit2. Rdy1. Rdy2. 1[i]. N. 2[*1]. Y. Mult. F0. F2. F4. No. Yes. - PowerPoint PPT Presentation
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2. Function Unit StatusFU Busy Op Dest Sop1 Sop2 Unit1 Unit2 Rdy1 Rdy21[i] N2[*1] Y Mult F0 F2 F4 No Yes3[*2] N4[+] Y Add F6 F8 F2
5[/] Y Div F10 F0 F6 2[*1] No Yes
Registers: F0 F2 F4 F6 F8 F10FU# 2[*1] 4[+] 5[/]
3. Register Result Status
The ADDF is Next to Complete. The changes are noted in Red.
1. Instruction Status QueueInstruction Issued Op Read Ex Cmpl ResultLF F6,34(R2) X X X XLF F2,45(R3) X X X XMULTF F0,F2,F4 X XSUBF F8,F6,F2 X X X XDIVF F10,F0,F6 XADDF F6,F8,F2 X X X
QuestionADDF will try to write back. Why can it not do this now?
* *
AnswerADDF tries to write back to F6, but since the DIVF instruction has not yet read its operands (WAR), the scoreboarding technique will stall the write back until DIVF has read its operands.1. Instruction Status QueueInstruction Issued Op Read Ex Cmpl ResultLF F6,34(R2) X X X XLF F2,45(R3) X X X XMULTF F0,F2,F4 X XSUBF F8,F6,F2 X X X XDIVF F10,F0,F6 XADDF F6,F8,F2 X X X
2. Function Unit StatusFU Busy Op Dest Sop1 Sop2 Unit1 Unit2 Rdy1 Rdy21[i] N2[*1] Y Mult F0 F2 F43[*2] N4[+] Y Add F6 F8 F2
5[/] Y Div F10 F0 F6 2[*1] No Yes
Registers: F0 F2 F4 F6 F8 F10FU# 2[*1] 4[+] 5[/]
3. Register Result Status
The MULTF Finally Completes.The changes are noted in Red.
1. Instruction Status QueueInstruction Issued Op Read Ex Cmpl ResultLF F6,34(R2) X X X XLF F2,45(R3) X X X XMULTF F0,F2,F4 X X XSUBF F8,F6,F2 X X X XDIVF F10,F0,F6 XADDF F6,F8,F2 X X X
* *
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2. Function Unit StatusFU Busy Op Dest Sop1 Sop2 Unit1 Unit2 Rdy1 Rdy21[i] N2[*1] N3[*2] N4[+] Y Add F6 F8 F25[/] Y Div F10 F0 F6 Yes Yes
Registers: F0 F2 F4 F6 F8 F10FU# 4[+] 5[/]
3. Register Result Status
The MULTF Writes Results.The changes are noted in Red.
1. Instruction Status QueueInstruction Issued Op Read Ex Cmpl ResultLF F6,34(R2) X X X XLF F2,45(R3) X X X XMULTF F0,F2,F4 X X X XSUBF F8,F6,F2 X X X XDIVF F10,F0,F6 XADDF F6,F8,F2 X X X
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2. Function Unit StatusFU Busy Op Dest Sop1 Sop2 Unit1 Unit2 Rdy1 Rdy21[i] N2[*1] N3[*2] N4[+] Y Add F6 F8 F2 * *5[/] Y Div F10 F0 F6 * *
Registers: F0 F2 F4 F6 F8 F10FU# 4[+] 5[/]
3. Register Result Status
The DIVF can now read its operands.The changes are noted in Red.
1. Instruction Status QueueInstruction Issued Op Read Ex Cmpl ResultLF F6,34(R2) X X X XLF F2,45(R3) X X X XMULTF F0,F2,F4 X X X XSUBF F8,F6,F2 X X X XDIVF F10,F0,F6 X XADDF F6,F8,F2 X X X
2. Function Unit StatusFU Busy Op Dest Sop1 Sop2 Unit1 Unit2 Rdy1 Rdy21[i] N2[*1] N3[*2] N4[+] N5[/] Y Div F10 F0 F6 * *
Registers: F0 F2 F4 F6 F8 F10FU# 5[/]
3. Register Result Status
The ADDF writes results and DIVF starts.The changes are noted in Red.
1. Instruction Status QueueInstruction Issued Op Read Ex Cmpl ResultLF F6,34(R2) X X X XLF F2,45(R3) X X X XMULTF F0,F2,F4 X X X XSUBF F8,F6,F2 X X X XDIVF F10,F0,F6 X XADDF F6,F8,F2 X X X X
2. Function Unit StatusFU Busy Op Dest Sop1 Sop2 Unit1 Unit2 Rdy1 Rdy21[i] N2[*1] N3[*2] N4[+] N5[/] N
Registers: F0 F2 F4 F6 F8 F10FU#
3. Register Result Status
The DIVF will finish execution and write its results. The changes are noted in Red.
1. Instruction Status QueueInstruction Issued Op Read Ex Cmpl ResultLF F6,34(R2) X X X XLF F2,45(R3) X X X XMULTF F0,F2,F4 X X X XSUBF F8,F6,F2 X X X XDIVF F10,F0,F6 X X X XADDF F6,F8,F2 X X X X
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