PicoJava Microprocessor Architecture

1. King Fahd University of Petroleum and Minerals College of Computer Science and Engineering Computer Engineering Department COE -390 : Seminar PicoJava Microprocessor Architecture Presented by Muhammad F. Sagr

2. Contents • Java Virtual Machine • 3 Ways to Execute Java Code • PicoJava Overview • PicoJava Structural Implementation • The Stack Cache • Cost and Performance PicoJava Microprocessor Architecture – Muhammad Sagr Page 2 of 40

3. Java Virtual Machine(A Machine within a Machine) System Calls PicoJava Microprocessor Architecture – Muhammad Sagr Page 3 of 40

4. 3 Ways to Execute Java Code PicoJava Microprocessor Architecture – Muhammad Sagr Page 4 of 40

5. PicoJava Chip PicoJava Microprocessor Architecture – Muhammad Sagr Page 5 of 40

6. PicoJava Structural Implementation PicoJava Microprocessor Architecture – Muhammad Sagr Page 6 of 40

7. Stack cache • The stack cache is a 64 entry register file which caches the top few entries of the operand stack. • Stack is circular. 65 pushes would result in one cache replacement. PicoJava Microprocessor Architecture – Muhammad Sagr Page 7 of 40

8. PicoJava Features • Developed Using Verilog RTL. • Supports: • Hardware floating-point arithmatics. • 6-digit instruction pipeline. • Instruction / Data Caching. • Innovative Stack Management Unit. • Stack-based architecture: • Has no General-purpose Registers • Allows up to 2 POP and 1 PUSH per clock cycle. PicoJava Microprocessor Architecture – Muhammad Sagr Page 8 of 40

9. JVM and PicoJava • Data types: byte, short, int, long, float, double, char, object, returnAddress • All opcodes have 8 bits followed by a variable number of operands (1,2,3…) • Opcodes • 200 assigned • 24 quick variations • 2 reserved PicoJava Microprocessor Architecture – Muhammad Sagr Page 9 of 40

10. JVM Code Size • Compact Code • Average JVM instruction is 1.8 bytes • RISC instruction required 4 bytes • Java based bytecodes are smalls • No register specifiers • Implicit “VARS” register for local variable accesses • Large application (2500+ lines) coded both the C++ and Java Languages • Java bytecodes are 2 – 3 x smaller than the RISC code from the C++ complier PicoJava Microprocessor Architecture – Muhammad Sagr Page 10 of 40

11. PicoJava Microprocessor Overview • Pipeline instructions. • Single cycle execution for most instructions. • Implement in hardware only those instructions that make a difference. • Trap for costly instruction that do not occur often. PicoJava Microprocessor Architecture – Muhammad Sagr Page 11 of 40

12. PicoJava 4-Stage Pipeline • Figure 2 Simple 4 stage pipeline FETCH Fetch fixed Cache lines (from I/O via Instruction Cache) into the Instruction Buffer. DECODE Decode and apply folding Logic, if Appropriate. EXECUTE Execute for one Or more cycles. WRITE-BACK Write results back Into the operand’s Stack. PicoJava Microprocessor Architecture – Muhammad Sagr Page 12 of 40

13. Stack-Based Architecture • Stack architecture implement as a RISC • Operands typically accessed from the stack, put back on the stack • Example: Integer addition • Add top 2 entries in the stack and put the result back on top of the stack • Typical emulation on a RISC processor • LOAD TOS • LOAD TOS-1 • ADD • STORE TOS-1 PicoJava Microprocessor Architecture – Muhammad Sagr Page 13 of 40

14. PicoJava: Performance and cost • Embeded market products (mobile phones etc) very sensitive to systems cost • Eliminates interpreter or JIT • Excellent systems performance compare to other processor ( Pentium etc.) • Efficient implementation through use of the same methodology; process circuit techniques developed for RISC processors PicoJava Microprocessor Architecture – Muhammad Sagr Page 14 of 40

15. PicoJava: Performance and cost • Simple and very efficient • Accelerates runtime • Support for garbage collection • Support for threads PicoJava Microprocessor Architecture – Muhammad Sagr Page 15 of 40

16. Comparison of PicoJava and Pentium chips Fig. 6 PicoJava Microprocessor Architecture – Muhammad Sagr Page 16 of 40

17. Conclusion • PicoJava is used in internet appliances, WebTV, mobile phones and other high speed appliances. • In the very near future, PicoJava will be a processor of choice for CPUs. • PicoJava achieved speed and efficiency. • Five major companies are already licensed for PicoJava chips. PicoJava Microprocessor Architecture – Muhammad Sagr Page 17 of 40

18. References • PicoJava Microprocessor Core Architecture: http://www.cs.ualberta.ca/~macg/C429/Extras/picoJava.htm • Sun Microsystems: http://www.sun.com PicoJava Microprocessor Architecture – Muhammad Sagr Page 18 of 40

19. Thank you! ? ? ? Questions? ? ? ? PicoJava Microprocessor Architecture – Muhammad Sagr Page 19 of 40