2. Integrated Circuits Costs IC cost = Die cost + Testing cost + Packaging cost Final test yield Die cost = Wafer cost Dies per Wafer * Die yield Dies per wafer = š * ( Wafer_diam / 2)2 – š * Wafer_diam – Test dies Die Area ¦ 2 * Die Area Die Yield = Wafer yield * 1 +  Defects_per_unit_area * Die_Area  } { Die Cost goes roughly with die area4

3. Real World Examples Chip Metal Line Wafer Defect Area Dies/ Yield Die Cost layers width cost /cm2 mm2 wafer 386DX 2 0.90 $900 1.0 43 360 71% $4 486DX2 3 0.80 $1200 1.0 81 181 54% $12 PowerPC 601 4 0.80 $1700 1.3 121 115 28% $53 HP PA 7100 3 0.80 $1300 1.0 196 66 27% $73 DEC Alpha 3 0.70 $1500 1.2 234 53 19% $149 SuperSPARC 3 0.70 $1700 1.6 256 48 13% $272 Pentium 3 0.80 $1500 1.5 296 40 9% $417 • From "Estimating IC Manufacturing Costs,” by Linley Gwennap, Microprocessor Report, August 2, 1993, p. 15

4. Learning Curve • “When volume doubles, cost reduces 10%” • Gordon Bell 1978 • Example: PCs v. Workstations 1990 1992 1994 1997 PC 24M 33M 44M 65M WS .41M .58M .68M .98M Ratio 59 57 65 67 • 65x ~ 2^6 --> .9^6 = 0.53

5. A B C D Pipelining: Its Natural! • Laundry Example • Ann, Brian, Cathy, Dave each have one load of clothes to wash, dry, and fold • Washer takes 30 minutes • Dryer takes 40 minutes • “Folder” takes 20 minutes

6. A B C D Sequential Laundry 6 PM Midnight 7 8 9 11 10 Time • Sequential laundry takes 6 hours for 4 loads • If they learned pipelining, how long would laundry take? 30 40 20 30 40 20 30 40 20 30 40 20 T a s k O r d e r

7. 30 40 40 40 40 20 A B C D Pipelined LaundryStart work ASAP 6 PM Midnight 7 8 9 11 10 Time • Pipelined laundry takes 3.5 hours for 4 loads T a s k O r d e r

8. 30 40 40 40 40 20 A B C D Pipelining Lessons 6 PM 7 8 9 • Pipelining doesn’t help latency of single task, it helps throughput of entire workload • Pipeline rate limited by slowest pipeline stage • Multiple tasks operating simultaneously • Potential speedup = Number pipe stages • Unbalanced lengths of pipe stages reduces speedup • Time to “fill” pipeline and time to “drain” it reduces speedup Time T a s k O r d e r

9. Computer Pipelines • Execute billions of instructions, so throughout is what matters • DLX desirable features: all instructions same length, registers located in same place in instruction format, memory operands only in loads or stores

10. Example: MIPS (­ DLX) Register-Register 6 5 11 10 31 26 25 21 20 16 15 0 Op Rs1 Rs2 Rd Opx Register-Immediate 31 26 25 21 20 16 15 0 immediate Op Rs1 Rd Branch 31 26 25 21 20 16 15 0 immediate Op Rs1 Rs2/Opx Jump / Call 31 26 25 0 target Op

11. 5 Steps of DLX DatapathFigure 3.1, Page 130 Instruction Fetch Instr. Decode Reg. Fetch Execute Addr. Calc Memory Access Write Back IR L M D

12. Pipelined DLX DatapathFigure 3.4, page 137 Instruction Fetch Instr. Decode Reg. Fetch Execute Addr. Calc. Write Back Memory Access • Data stationary control • local decode for each instruction phase / pipeline stage

13. Visualizing PipeliningFigure 3.3, Page 133 Time (clock cycles) I n s t r. O r d e r

14. Its Not That Easy for Computers • Limits to pipelining: Hazards prevent next instruction from executing during its designated clock cycle • Structural hazards: HW cannot support this combination of instructions (single person to fold and put clothes away) • Data hazards: Instruction depends on result of prior instruction still in the pipeline (missing sock) • Control hazards: Pipelining of branches & other instructionsstall the pipeline until the hazardbubbles” in the pipeline