CSCE 430: Computer Architecture

Final Project

Group E:Matt HornDongpu JinNick

BrigantiSean Hicks

Overview

Overview3 stage pipelineLCD panel outputStatic “branch not taken” predictorWrite through Instruction and Data CachesVersatile assembler for rapid development

PipelineThree stages pipeline

IF/IDEXMEM/WB

Two pipeline registersID/EX registerEX/MEM register

PipelineSave both signal and data for next stageSynchronousClock in values on the rising edge

Clock cannot be too fast, because of tsu and th

Forwarding UnitData hazards happens because of data

dependency lw r1 0addi r2 r1 2

Need to forward value for lw directly to ALU source

Forwarding UnitIF (WRITE) and (rt = Dest) then ForwardA =

1IF (WRITE) and (rd= Dest) then ForwardB =

1

Hazard Detection

• Handles cases where Forwarding Unit is not enough-- Ex: lw $s0 0($0)

add $s2 $s0 $s1• Inserts Noops by deasserting control signals and stalls PC in order to halt pipeline

Branch Predictor• Static “Branch not Taken” predictor

• Deasserts control signals for pipeline when a branch is taken

Otherwise, instructions continue to execute• Penalty for correct branch = 0 cycles• Penalty for an incorrect branch = 2 cycles

Instruction Cache16 sets, 4 words/blockDirect mappedAddress Breakdown

4 bit tag4 bit index2 bit offset

8 cycle penalty

Instruction Cache

Data CacheSame specs as

instruction cache except2 bit tag

Write-through policy8 cycle delay for read

miss9 cycle delay for write

miss

Data Cache

Overall Verification

LCD Panel Includes 128 words which mirror data

memory Handles most user IO for the board

User selects location 0-127 with switches LCD Panel displays MEM[0-127]

LCD Panel Advantages of LCD memory mirroring data

Simplifies program development Aids debugging on the board

Disadvantages Less versatile, displayed data must appear in

memory locations 0-127

Assembler Final instruction set

Instruction Type Syntax Opcode Function

Add R Add $rd $rs $rt 0 32

Sub R Sub $rd $rs $rt 0 34

And R And $rd $rs $rt 0 36

Or R Or $rd $rs $rt 0 37

Add Immediate I Addi $rs $rt imm 8 --

Load Word I Lw $rt imm $rs 35 --

Store Word I Sw $rt imm $rs 43 --

Branch if Equal I Beq $rs $rt imm 4 --

Branch if Not Equal I Bne $rs $rt imm 5 --

Jump J J label 2 --

Jump and Link J jal label 3 --

Assembler

Data driven, ISA parsed before assembly Instruction set Tokens Registers

Assembler - Instructions add rd,rs,rt; op=0, rs, rt, rd, shamt=0,

funct=32 addi rs, rt, imm; op=8, rt, rs, imm lui rs, imm; op=15, rs, rt=0, imm bne rs, rt, imm; op=5, rs, rt, ~imm jal label; op=3, label jr rs; op=0, rs, rt=0, rd=0,

shamt=0, funct=8

Assembler - Tokens rd 5 rs 5 rt 5 op 6 imm +16 label +26 shamt 5 funct 6

Assembler - Registers zero 0 0 0 at 1 v0 2 v1 3 a0 4 a1 5 a2 6 a3 7 t0 8

Assembler - Output # Reads memory location 0,

then sorts that many numbers in the following memory values 1-n

main: lw $s1 0 $0 # load

memory location 0 into $s1 addi $s1 $s1 1 #

increment $s1 for comparison with our "for" loop

outer: addi $s0 $0 0 # s0 is != 0 if

a value has been changed during a bubble sort sweep

addi $s2 $0 1 # s2 holds the current outer iteration of bubble sort

BEGIN0: 8C110000; -- lw 17 0 0 1: 22310001; -- addi 17 17 1 2: 20100000; -- addi 16 0 0 3: 20120001; -- addi 18 0 1 4: 20120001; -- addi 18 0 1 5: 8E48FFFF; -- lw 8 -1 18 6: 8E490000; -- lw 9 0 18 7: 01285022; -- sub 10 9 8 8: 3D608000; -- lui 11 -

32768 9: 016A6024; -- and 12 11 10

Questions?