ALU. Announcements. Lecture 9. Pipeline Hazards. Review: Single-cycle Datapath (load instruction) Review: Multi-cycle Datapath. R e g s.

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1 Aoucm Lcu 9 Pipli Haza Chio Kozyaki Safo Uiviy hp://cla.afo.u/8b PA- i u oay Elcoic ubmiio Lab2 i u o Tuay 2/3 h Quiz ga will b availabl wk Soluio will b po o li omoow Tuay 2/3 h lcu will b a vio playback Ca com o lcu hall o wach fom hom o offli 2 Rviw: Sigl-cycl Daapah (loa iucio) Rviw: uli-cycl Daapah F: ucio Fch Fch h iucio fom mmoy cm h PC by 4 RF/D: Rgi Fch a ucio Dco Fch ba gi EX: Ecu Calcula ba + ig- immia E: moy Ra h aa fom h aa mmoy : Wi back Wi h ul back o h gi fil Clk P C Divi aapah io p Each p i o clock cycl No RF i a ho cycl, bu wai fo clock F ucio Fch. moy RF Rgi Fch R g EX Ecuio E. moy Daa moy Wi back R g Loa 3 4

2 Rviw: Full Pipli Rviw: Pipliig Loa Fch a w iucio ach cycl Each ag of h pipli i wokig o a iff iucio F ucio Fch RF Rgi Fch EX Ecuio E. moy Wi back Loa iucio ak 5 ag Fiv ip fucioal ui wok o ach ag Each fucioal ui u oly oc Aoh loa ca a a oo a fiih F ag Each loa ill ak 5 cycl o compl Th houghpu, howv, i much high. moy R g Daa moy R g Clock lw Cycl Cycl 2 Cycl 3 Cycl 4 Cycl 5 Cycl 6 Cycl 7 2 lw 3 lw 5 6 Pipli Daapah poa SA u PC 4 F D EX E u ucio mmoy F/D D/EX EX/E E/ ucio Ra gi Ra gi 2 Rgi Wi gi Wi aa 6 Ra aa Ra aa 2 Sig 32 Shif lf 2 u ul Zo ul Wi aa Daa mmoy Ra aa u ucio lgh Fi PS iucio lgh allow ay pipli v hough co o o happ uil h co ag l 886 ha a much mo challgig poblm wh iucio vay fom -7 by ucio foma Rgi acc poibl v hough co o o happ uil co ag u o gulaiy of foma Limi mmoy acc Sic oly loa a o acc mmoy, oh iucio o o o u h o calcula h mmoy a bfo h acual compuaio 7 8

3 Rviw: Cool Sigal Rviw: ulilvl Dcoig fuc No poa op a ub oi lw w bq jump RgD Sc morg RgWi mwi Bach Jump Ep c<2:> Sub Sub Sic oly h h fuc fil Pa i o h ui, a hav a local co h op 6 ai Cool fuc 6 op N Cool (Local) c 3 9 Pipli Cool Cool Sigal N o cool fucioal ui Bu hy a fom wokig o iff iucio! No a poblm Ju pipli h cool igal alog wih h aa ak u hy li up Uig lablig covio of hlp ucio_f ma hi iucio i i RF Evy im i g flopp, chag pipag ak u igh igal go o h igh plac U a ai Cool ui o ga igal uig RF/D Sag Cool igal fo EX (Ep, Sc, ) u cycl la Cool igal fo m (mw, Bach) u 2 cycl la Cool igal fo (morg, mw) u 3 cycl la 2

4 plmig Cool Puig i All Togh PCSc D/EX RF/D EX E u Cool EX/E E/ F/D EX F/D Rgi ai Cool Ep Sc p RgD mw Bach morg RgW D/E Rgi Ep Sc p RgD mw Bach morg RgW E/E Rgi mw Bach morg RgW E/ Rgi morg RgW _f mm _wb PC 4 ucio mmoy ucio Ra gi Ra gi 2 Rgi Wi gi Wi aa ucio [5 ] ucio [2 6] ucio [5 ] RgWi Ra aa Ra aa Sig Shif lf 2 6 u u cool RgD ul Sc p Zo ul Bach Wi aa mwi Daa mmoy Ra aa mra morg u 3 4 Compaio Cycl Cycl 2 Clk Sigl Cycl plmaio: Loa So Wa Bu Somhig Fihy H f iviig i io 5 pa ma h clock fa A h ffciv CP i ill o Clk Cycl Cycl 2 Cycl 3 Cycl 4 Cycl 5 Cycl 6 Cycl 7 Cycl 8 Cycl 9 Cycl Th iviig i io pa woul mak h clock v fa A woul h CP ill b o? ulipl Cycl plmaio: Loa So R-yp F Rg EX E F Rg EX E F Pipli plmaio: Loa F Rg EX E So F Rg EX E R-yp F Rg EX E 5 Th why o go o wy cycl? Rally wo iu Som hig ally hav o compl i a cycl Fi PC fom cu PC CP i o ally o Somim you h ul fom h pviou iucio 6

5 Pipli Haza Sucual Haza Th a pci bw iucio ha a po by pipliig Cau pipli o loo fficicy (pipli all, wa cycl) f all iucio a p No avaag of a pipliig (ic all mu wai) Th limi o pipliig a kow a haza Sucual Haza (Rouc Coflic) Two iucio o u h am pic of hawa Daa Haza ucio p o ul of iucio ill i h pipli Cool Haza ucio fch p o h ul of iucio i pipli Rouc coflic ccu wh wo iucio y o u am hawa f ai wh om fucioal ui i o fully pipli To avoi ucual haza: U ouc oc p iucio Alway i h am cycl, o hi aagm i ba: Loa u Rgi Fil Wi po uig i 5 h ag Loa R-yp u Rgi Fil Wi po uig h 4 h ag R-yp F RF/D EX 7 8 Sucual Haza Eampl Sucual Haza Soluio Coi a loa follow immialy by a opaio Rgi fil oly ha a igl wi po Bu o wi h ul of h a h mmoy back Clock R-yp Cycl Cycl 2 Cycl 3 Cycl 4 Cycl 5 Cycl 6 Cycl 7 Cycl 8 Cycl 9 F RF/D EX R-yp F RF/D EX Loa F RF/D EX R-yp op! W hav a poblm! F RF/D EX Follow icio Alway u ouc a h am im i ach iucio Buil mo compl fucioal ui Fo ampl uppo wo wi io gi fil Bu h you woul pobably wa o mak u of hi fau i oh way, a you pobably ill woul lik o follow icio Dlay offig iucio (quu up o u h ui) U wh ui a o fully pipli (mul, iv) Hawa i a pipli all(bubbl) ha lay offig iucio ca CP fom h ial valu of 9 2

6 Dlay Wi Back Soluio Ai (ki of): Daa Dpci Dlay R-yp gi wi by o cycl Do hi ica h CP of iucio? Wha i h co? Clock R-yp Cycl Cycl 2 Cycl 3 Cycl 4 Cycl 5 Cycl 6 Cycl 7 Cycl 8 Cycl 9 R-yp R-yp Loa R-yp R-yp 2 Wh a compil i gaig co of i o o co o mak pipli machi fa o mak u ha h w co quc h am a h ol co quc Wh ca i o iucio? Wh h w o o o viola ay aa pci bviou iu i a af wi (u pc) N o pouc valu bfo aig i Bu h a oh a wll WAW WAR 22 Daa Haza Typ Dpcy Eampl Daa pci fo iucio j followig iucio i Ra af Wi (RAW) (u pc) ucio j i o a bfo iucio i i o wi i Wi af Wi (WAW) (oupu pc) ucio j i o wi a opa bfo i wi i valu Wi af Ra (WAR) (ai pc) ucio j i o wi a iaio bfo i i a by i No uch hig a a Ra af Ra (RAR) haza ic h i v a poblm aig wic Tu pcy => RAW haza au $, $, $2 ubu $3, $4, $ upu pcy => WAW haza au $, $, $2 ubu $, $4, $5 Ai pcy => WAR haza au $, $, $2 ubu $, $4, $

7 Daa Haza Daa Haza Eampl Th co of h aiioal cycl Pogamm hik iucio cu i o cycl N o maiai ha illuio v wh pipliig f h gi a a wi occu i iff pip ag f a a aly a wi a la Pogamm pc h pviou iucio hav fiih Thy pc h w valu Bu h gi fil ha h ol valu Viola h RAW pc Ca hav WAW o WAR haza ul: Wi occu i iff cycl fo iff iucio, o a ca occu af wi fo a iucio Nih gally happ i fiv ag pipli Dpci backwa i im a haza. Tim (clock cycl) F D/RF EX E a,2,3 ub 4,, 3 a 6,, 7 o 8,, 9 o,, Rg Dm Rg Rg Dm Rg Daa Haza Soluio Daa Haza - Sall Fo RAW haza, You o lay iucio uil aa i availabl pio How o wai Wh o you cla h aa i availabl Talk abou hi oo How o wai how o all h pipli Hav h ofwa i NP o hi poblm o o occu Ca hawa ha all h pipli Dyamically ca h NP Pipli ilock o machi will all if Bu h compil i o miimiz all 27. Elimia v im pcy by allig Tim (clock cycl) F D/RF EX E a, 2, 3 ub 4,, 3 a 6,, 7 o 8,, 9 o,, bubbl bubbl bubbl Rg Dm Rg 28 Rg Dm Rg Rg

8 Pfomac Effc Rucig Sall Sall ca hav a igifica ffc o pfomac Coi h followig ca Th ial CP of h machi i A RAW haza cau a 3 cycl all f 4% of h iucio cau a all? Th w ffciv CP i = 2.2 A h al % i pobably high ha 4% You g l ha ½ h i pfomac! Ky i big caful abou wh you ay aa i availabl ou impl mol Cycl af Eai fom hawa, bu low Sic RF acc a fa, W ca allow aa o flow hough gi fil f you a a gi wh i i big wi, you g w valu aum wi uig ½ of cycl, a uig 2 ½ Now you all oly 2 cycl 29 3 Daa Haza Rgi Fil Pfomac Effc Rgi fil wi o fi half a a o co half. Tim (clock cycl) F D/RF EX E a, 2, 3 ub 4,, 3 a 6,, 7 o 8,, 9 o,, 3 bubbl bubbl Rg Dm Rg Rg Dm Rg Rg Sall ca hav a igifica ffc o pfomac Coi h followig ca Th ial CP of h machi i A RAW haza cau a 2 cycl all f 4% of h iucio cau a all? Th w ffciv CP i =.8 A h al % i pobably high ha 4% You g a lil mo ha ½ h i pfomac! 32

9 Rucig Sall o p byo Daa Haza - Fowa Ky i big caful abou wh you ay aa i availabl Fowa h aa o h appopia ui Bu you ally hav h valu i h machi a of f you ca u hi valu, h all fo i zo! Fa, bu qui mo hawa call fowaig. Tim (clock cycl) F D/RF EX E a, 2, 3 ub 4,, 3 a 6,, 7 o 8,, 9 o,, Rg Dm Rg Fowaig Limiaio Daa Haza wih Fowaig Ca fowa aa you o hav Sic compl i a cycl Alway hav ul fo h iucio moy o o u uil h of E Tha i o cycl la ha So iucio ca g h mmoy ul i o i h poco y u all h iucio uil h aa u Wih fowaig No -o- lay cycl loa-o- lay Daa i o availabl y o b fowa. Tim (clock cycl) lw, (2) ub 4,, 6 a 6,, 7 o 8,, 9 F D/RF EX E Rg Dm Rg 35 36

10 Hawa Sall Quio A pipli ilock chck a op h iucio iu. Tim (clock cycl) F D/RF EX E lw, (2) ub 4,, 3 a 6,, 7 o 8,, 9 Rg bubbl Dm Rg bubbl Rg Dm Rg Rg Dm Rg Wha happ if w hav wo fo ach iucio i u o ga ffciv a (uig ) i u o ga ul uig E Wha all o hi machi hav? P C F ucio Fch. moy RF Rgi Fch R g EX Ecuio E. moy Daa moy Wi back R g Nw Pipli Daa Haza wih Fowaig l pipli wa: F RF EX E F RF EX E F RF EX E Thi ma h wa a lay lo af a loa iucio Nw pipli (qui wo a) i F RF EX F RF EX F RF EX Now mmoy fch i pfom uig EX pha No lo af a loa Wha happ ow?. Tim (clock cycl) lw, (2) ub 4,, 6 a 6,, 7 o 8,, 9 F D/RF EX E Rg Rg Rg Rg Rg Rg 39 4

11 Pipli Eampl Pipli Eampl (co) l pipli: lw 4 8() F RF EX E (lo) F RF EX E a 2, 4, F RF EX E Nw pipli (qui wo a) i lw 4 8() F RF EX a 2, 4, F RF EX l pipli: a, 2, 3 F RF EX E lw 4 8() F RF EX E Nw pipli (qui wo a) i a, 2, 3 F RF EX (lo) F RF EX lw 4 8() F RF EX Which i b? Dp o which pai of iucio happ mo of 4 42 Fowaig Hawa Fowa Hawa - Daapah Wha o fowaig co? N o a uff o aapah a uff o cool Daapah N o a mulipl o fucioal ui Souc o fucio ui coul com fom Rgi fil moy of la cycl fom wo cycl ago ig hi mu ica h ciical pah of ig N o b ig cafully D/EX EX/E E/ ua ub Daa moy 43 44

12 Fowa Hawa - Cool Compil N o ci which mulipl ipu o abl Do m ha ha bu i ca g oublom Epcially wih machi ha iu mulipl iucio/cycl Which i h coc ul N o ag, E ul wih gid N o compa gi fch wih ag All hi ak hawa, bu ca b o i paalll N o fi youg vio of h gi ulipl ag ca mach N o fi fh vio of h aa Compil aag co o y o fill lo wih uful uff Fill loa lay lo wih a goo iucio Wh uccful, h lo ha o co Th iucio o o p o loa ul Do o o all Show h avaag of h pipli Wh ca fill h lo N o oupu a NP if h i o hawa ilock Sic h pipli i vy machi p N hawa ilock o u ol co o machi hav ilock! icopoco wihou lock Pipli Sag Raag Co Cool Haza Compil i ip iucio. Tim (clock cycl) F D/RF EX E lw, (2) ula iucio ub 4,, 3 a 6,, 7 o 8,, 9 Rg Dm Rg Th miig aa o fa ha b a ul U by aoh iucio Wha happ wh h miig aa i h iucio poi? Thi i call a cool haza Cool haza: Bach iucio f a bach i o ak h cool imply coiu wih PC + 4 f h bach i ak, h h PC jump o a w a Whh h bach i o b ak, howv, i ow kow uil h 3 (E) ag Jump iucio Cau a ga pfomac poblm ha aa haza ucio fch happ vy aly i h pipli 47 48