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Forth ReportE d i t o r : Paul Frengel; P.O. Box 820506, Houston, TX 77282; pfrenger@ix.netcom.com

Para l le l For t hPaul F renger

1 I n t r o d u c ti o n : C r a n k i n g U p t h eO l d C e n t r a l P r o c e s s o r

T h e m a j o r i t y o f d i g it a l c o m p u t e r s u s e d o n t h i s p l a n e t r u nth e i r p ro g ra m s s e q u e n t i a l ly . T h a t i s , t h e y f e t c h a n in -s t ru c t io n f r o m m e m o r y , d e c o d e i t, t h e n e x e c u t e t h e o p -e r a t io n s e m b o d i e d i n t h e n s t r u ct i o n . T h i s s i m p l e c y c l e isr e p e a te d o n a n d o n u n t i l t h e o m p u te r i s h a l t e d . T h i s k in do f c o m p u t e r i s s o m e t i m e s d e s c r i b e d a s a V o n N e u m a nm a c h i n e , a f t e r J o h n L o u i s v o n N e u m a n n ( 1 9 0 3 - 1 9 5 7 ) , am a t h e m a t i c i a n a n d p r o m o t e r o f t he s t o r e d c o m p u t e r p r o -g r a m c o n c e p t [ 1 ]. I t ' s a g r e a t d e s i g n , r o b u s t a n d e f f e c -t iv e . H o w e v e r , i t s s e q u e n t i a l a rc h i t e c tu re a c t s a l o t l i k et h e e s c a p e m e n t m e c h a n i s m i n a c l o c k , h o l d i n g b a c k c e n -t r a l p ro c e s s o r s p e e d in a t i c k - to c k g a i t. T h i s h a s b e e nr e f e r r ed to a s t h e ' V o n N e u m a n b o t t l e n e c k ' [ 2 ]. S i n c ep e o p l e u s u a l ly d o n ' t l i k e to w a i t , e n g i n e e r s a n d c o m p u t e rs c i e n t i s t s h a v e im p ro v e d , e n h a n c e d a n d h o n e d th i s l i t -t l e s e q u e n ti a l c o m p u t i n g m a c h i n e c o n t i n u o u s l y o v e r th ey e a r s u s in g a v a r i e ty o f t e c h n iq u e s . O n e s t r a t a g e m h a sb e e n to r a i s e th e C P U c lo c k s p e e d ; w e s t a r t e d w i th a 4 . 7 7M H z I n t e l 8 0 8 8 in t h e I B M P C i n 1 9 8 3 , a n d n o w w e a r ee n j o y i n g 4 5 0 M H z P e n t i u m I I s , w i t h f a s t e r c h i p s o n t h en e a r h o r i z o n . R a i s in g C P U s p e e d i s a n o n - t r iv i a l t a s k ,h o w e v e r , s in c e e x t e n s i v e c h a n g e s t o c h i p g e o m e t r y , t ra n -s i s to r t e c h n o lo g y , s e m i c o n d u c t o r f a b r i c a t i o n m e t h o d s a n dp o w e r m a n a g e m e n t h a ve h a d t o b e m a d e . S o m e o f t h es eC P U c h i ps w o r k n e a r t h e l i m i t s o f h e a t t o l e r an c e ; o c c a -s i o n al l y o n e o v e r s t e p s t h e s e b o u n d s i n a s m o k y , s p a r k i n gd i sp l a y. E v e n p r i n t ed c i r c u i t b o a r d f a b r i c a t i o n t e c h n o l o g yh a s h a d d i f f i c u l ty k e e p in g u p w i th th e s e s u p e r - f a s t C P U s .

A n o t h e r C P U p e r f o r m a n c e - e n h a n c i n g s t r a t a g e m h a sb e e n w i d e n i n g o f o n - c h i p b u s e s an d w o r d w i d t h s . O u r1 9 8 3 P C u s e d a n 8 -b i t C P U , q u ic k ly g o in g to 1 6 -b i t s , t h e n3 2 a n d 6 4 -b i t s. T h e s e n e w w id e -b u s c h ip s c a n t a k e in a n ds p i t o u t m o r e b y t e s o f i n f o r m a t i o n f r o m m e m o r y ( a s i n -s t ru c t io n s o r d a t a ) i n a s in g le c y c le . U n fo r tu n a te ly , w id e rb u s e s c o m m i t m o r e o f t h e c h i p ' s i n t er n a l s i l ic o n a c r e a g et o s i g na l c o n d u c t i o n r a t h e r t h a n t o c o m p u t a t i o n a l u n i ts .

O t h e r s t r a t a g e m s h a v e b e e n u s e d t o f u r t h e r e n h a n c e

t h e m o d e r n c e n t r a l p r o c e s s o r ' s s p e e d a n d g e n e r a l p e r f o r -m a n c e : p i p e l i n i n g t e c h n o lo g y , p r o v i s i o n f o r l a r g e o n - c h i pc a c h e s , s c o r e b o a r d i n g , o u t - o f - o r d e r i n st r u c t io n e x e c u -t i on , m a t h c o p r o c e s s o r s , h a v i n g m u l t i p l e e x e c u t i o n u n it sa n d s o on . T e c h n o l o g i e s n o t - y e t i m p l e m e n t e d ( s u c h a sth re e -d im e n s io n a l a rc h i t e c tu re s ) a re w a i t in g in th e w in g s .B u t u l t i m a t e l y , t h e b o t t l e n e c k s i n V o n N e u m a n ' s m a -c h i n e m u s t a s s e r t t h e i r p e r f o r m a n c e l i m i t a t i o n s , j u s t a sth e s p e e d o f l i g h t i n a v a c u u m a f fe c t s s p a c e t r a v e l ( t h e' S t a r T r e k ' l e g e n d n o t w i t h s t an d i n g ) .

C a n w e c i r c u m v e n t t h i s e x e c u t i o n s p e e d p r o b l e ms o m e h o w ?

2 I n t r o d u c i n g P a r a l l e l i s m ,S o m e F o r th

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W h e n c h e a p o r s i m p l e i s t he c r i te r i o n , o n e o f s o m e t h i n gu s u a l ly s u f f ic e s. F o r e x a m p l e , y e a r s a g o M o t o r o l a s o l da si n g l e - b it C M O S C P U , t h e M C 1 4 5 0 0 B , w h i c h t h eyc a l l ed t h e ' B i t F i d d l e r ' [ 3 ]. H a r d l y m o r e t h a n an A L U ,t h i s 1 M H z 1 6 - p in I C h a d n o a d d r e s s b u s , r e c o g n i z e ds i x t ee n 4 - b i t o p c o d e s ( t w o o f w h i c h w e r e n o - o p s ! ) a n dp e r f o r m e d a r i t h m e t i c a n d b o o l e a n f u n c t i o n s o n o n e d a t ab i t at a t i m e . Y o u c o n f i g u r e d a M C 1 4 5 0 0 B s y s t e m b yc o n n e c t i n g a f r e e - r u n n i n g u p - c o u n t e r t o t h e a d d r e s s l in e so f a 4 -b i t w i de p r o g r a m E P R O M , a n d th e f o u r E P R O Md a ta l i n e s f e d th e C P U i t s i n s t ru c t io n s . Wh e n th e c o u n te rw a s r e s e t t o z e ro th e f i r s t i n s t ru c t io n w a s f e t c h e d f ro mt h e E P R O M , t h e n e x e c u t e d b y t h e M C 1 4 5 0 0 B . E a c h i n -s t ru c t io n in tu rn w a s f e t c h e d a s th e c o u n te r s i n c re m e n te d .W h e n t h e c o u n te r s o v e r f l o w e d t o z er o a g a i n , t he p r o g r a mr e s t ar t e d . I f y o u w e r e c l e v er w i th C M O S 4 0 0 0 - s e r i e sa n d 7 4 C - s e r i e s ' g l u e c h i p s ' , y o u c o u l d c r e a t e q u i t e c o m -p le x a n d s o p h i s t i c a t e d s y s t e m s w i th i t . Mo to r o la in t e n d e dt h e p a r t t o b e a s u p e r - s i m p l e p r o c e s s o r f o r s u c h a p p l i c a-t io n s a s t r a f f i c l i g h t s e q u e n c e r s , b u t s in g le -c h ip m ic ro -c o n t ro l l e r s w e re a h e c k u v a lo t e a s i e r t o u s e , a n d o n e o ft o d a y ' s M i c r o c h i p T e c h n o l o g i e s ' P I C 1 2 C - s e ri e s 8 - pi n 8 -b i t O T P c o n t ro l l e r s w o u ld ru n r in g s a ro u n d i t . S o , n o , I ' m

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Forthn o t s u r p ri s e d y o u n e v e r h e a r d o f t h e M C 1 4 5 0 0 B .

Wh i l e o n t h e su b j ec t o f s i n g l e -b i t s an d CP Us , M o to ro l aa l so c r ea t ed a ch eap v er s io n o f i t s 8 -b it 6 8 0 0 p ro cesso r a r -ch i t ec tu re , t h e 6 8 0 4 , wh ich ( i f I h ea rd t h is r i g h t ) u sed as in g l e -b i t i n t e rn a l s e r i a l b u s t o mo v e d a t a b y t es a ro u n do n t h e ch ip . Th i s se r i a l ap p ro ach was ab o u t e i g h t t imesslower than using t rad i t ional 8 -b i t paral lel data paths , bu td id m ee t t h e c r i t e r i o n o f sav in g ex p en s iv e s i l i co n fo r t ran -s i s t o r s s i n ce i t r eq u i r ed o n ly o n e s i g n a l co n d u c to r i n -t e rn a ll y . Bu t w i th s i li co n g eo m et r i es n o w sh r in k in g t on ear ly n o th in g an d m ic ro co n t ro l l e r s h i tt i n g 4 9 cen t s i nq u an t i t y ( as a r ecen t Z i l o g ad b rag g ed ) , t h e re i s n o j u s t i -f i ca t io n fo r a s lo w ch ea p ch ip w h en f as t ch eap ch ip s a r eavai lab le .

I h ad a t each e r i n sch o o l wh o u se d t o j u s t i fy g ro u ph o m e w o r k a s s i g n m e n t s b y s a y i n g " m a n y h a n d s m a k el i g h t wo rk " . Wel l t h ey d o , b u t t h e r esu l t i n g i n te rp er so n a lco n fu s io n can b e a k i ll e r. I n o u r d i scu ssio n t o d ay , I 'mg o in g t o p resen t a f ew ex am p les o f t h i s 'man y h an d s ' ap -p r o a c h f o r y o u r a m u s e m e n t a n d e d if i ca t io n .

A g o o d ex am p le o f p a ra l le l i sm was sh o w n to t h e at t en -d ees o f t h e 1 99 1 S IG F o r th Co n fe re n ce i n S an An to n io ,Tex as [4 ]. Th i s Dr H o we r to n h ad a s tu d en t i n h i s p ro -g ram min g l an g u a g es c l as s, a Jo sep h Grad eck i , wh o b u i l ta p a ra l le l co m p u te r u s in g s i x t een In t e l 8 0 3 1 8 -b i t mic ro -co n t ro l l e r s a r r an g ed i n a h y p erc u b e . Each 8 0 3 1 ' n o d e 'c o n t a in e d a h o m e - g r o w n F o r t h i n t e r pr e t er ; e a c h c o m -mu n ica t ed se r i a l l y wi th i t s n ea res t n e ig h b o r n o d es an dwi th a mas t e r CP U wh ich co n t ro l l ed t h e en t ir e h y p ercu b e .Jo sep h c r ea t ed a s imp le p a ra l l e l-OS b ased o n F o r th . Hed em o n s t r a t ed t h i s d ev i ce b y ca l cu l a t i n g M an d e lb ro t s e t s ,p e r fo rm in g p ara l le l t ex t s ea rch es an d p ip e l i n ed co mp u ta -t i o n o f p o ly n o m ia l s . W i th an 8 0 31 i n t e rn a l c l o ck sp eed o f3 M H z , t h e ' c u b e ' a c h i e v e d 1 9 2 M I P S a n d b e t w e e n 4 a n d8 m e g a F L O P S . T h i s i s e x c e l l e n t p e rf o r m a n c e , e s p e c ia l l yfo r su ch d in k y l i tt l e 8 -b i t co n t ro l l e r s , ten y ear s ag o ! An dag a in , u s in g t o d ay ' s m ie ro co n t ro l l e r s ( li k e th e S c en ix 5 0M H z v e r s io n o f t h e M i c r o c h i p T e c h n o l o g y P I C 1 6 C 5 x) ,y o u co u ld b u i l d a b ig , f a s t F o r th h y p ercu b e o n a s i n g l eE u r o c a r d b o a r d .

Heck , ev en I g o t i n to t h i s ac t , an d a t t h a t s ame ACMS I G F o r t h C o n f e r e n c e m e n t i o n e d a b o v e [5 ] . I d e s ig n e da m u l t i - la y e r n e u r a l n e t w o r k s y s t e m u s i ng N e w M i c r o s 'N M I S - 0 0 2 1 F o r t h - b a s e d M o t o r o l a 6 8H C 1 1 s i ng l e b o a rdco m p u te r s [6 ]. I c r ea t ed an 'A-n eu ro n ' an d a 'B - n eu ro n '(wh ich d i f f e r ed o n ly i n wh e th er t h e F o r th so f tware u sedth e 6 8 HC1 l ' s an a lo g o r d ig i t a l I /O) o n eac h 2 - i n ch b y4 - in ch CP U b o ard . Each b o ard s imu la t ed 8 h y b r id n eu -ro n s , wh ich were d i r ec t l y co n n e c t ed v e r t i ca l l y an d h o r i -zo n t a l l y to o th e r n eu ro n s i n t h e v a r i o u s l ay er s . Th e s im-

p l es t 3 - l ay er 8 -n eu ro n n eu ra l n e two rk co n s i s t ed o f twoNe w M icro s ' b o ard s , co n n ec t ed t o g e th er t o fo rm a 4 - i n chsq u are , o n e-h a l f - i n ch t al l. Ne tw o rk s co n t a in in g mo re l ay -e r s an d /o r mo re n eu ro n s co u ld b e as semb led u s in g mo reb o ard s , a l l co n t ro l l ed b y t h e F o r th l an g u ag e . Ob v io u s ly ,t h i s i s a d i f f e r en t k in d o f p a ra l l e li sm th an t h a t men t io n edab o v e ( a r ti f ic i a l an a lo g n eu ra l n e two rk v s . d ig it a l h y p er -cube) , bu t I th ink th is example i l lus t rates the p r incip leo k ay .

Nex t we ' r e g o in g t o j u m p p as t 8 -b i t p ro cesso r p o wer ,b u r s t in g i n to t h e r ea lm o f 1 6 -b it t o 3 2 -b i t n o d e n e two rk san d wel l b ey o n d .

3 M o r e P a r a l l el is m , M o r e F o r t hIn t h e ea r l y 1 9 8 0 ' s , n o w -g o n e INM O S crea t ed t h e irf i rs t Tran spute r CP U, the T-212 [3]. I t was a 16-b i ts t ack / accu m u la to r d es ig n wi th a RIS C- l i k e 'min im ized 'i n s t ru c t io n se t. W h at m ad e t h e T ran sp u t e r i d ea l fo r p a ra l -l e l p ro cess in g n e two rk s was i ts b u i l t - i n h a rd ware su p p o r t-i n g f a s t C P U - t o - C P U c o m m u n i c a t io n s . E a c h T r a n s p u te rch ip h ad fo u r h ig h - sp eed se r i a l d a t a l i n k s wi th o n -ch ipRA M b u f fe r s an d DM A p ro cess in g , so t h a t i n t e rp ro ces -so r co mmu n ica t i o n s wo u ld t ak e p l ace i n a b ack g ro u n dmo d e , n o t r eq u i r in g co n s t an t CP U su p erv i s io n .

INM OS d ev e lo p ed t h e T ran sp u t e r t h ro u g h 3 2 -b i t v e r -s ions (T-414 and T-800) and a 64-b i t bus vers ion ( the T-9 0 0 0 ) . Th e T -8 0 0 h ad an i n t e rn a l 6 4 -b i t fl o a t in g p o in tAL U, so m ewh a t r emin i sce n t o f th e In te l 4 8 6 . Th e T -9 0 0 0 a l so ad d ed a 5 0 M Hz c lo ck , mu c h f as t e r p ro cess -i n g sp eed , a 1 6 k b y t e cach e , mo re h a rd ware co m mu n ica -t ions suppo r t and a 5 -s tage ins t ruct ion p ipel ine. Ins t ruc-t i o n s were b y t e co d e d (4-b i ts fo r co m ma n d s an d 4 -b i t s fo rd a t a o r wo rk s p ace o f f se t s ) , so a s i n g le 6 4 -b i t me mo ry ac -cess co u ld p i ck u p e ig h t o p co d e s a t a t ime wh ich t h e CP Uco u ld ex e cu t e i n p a ra ll e l . Th i s p a r t i cu l a r T ran sp u t e r wasid ea l fo r p a ra l l e l sy s t ems k n o wn as ' sy s to l i c a r r ay s ' . T h eT-9 0 0 0 , co mb in ed wi th C1 0 4 c ro ssb ar swi t ch es , co u ldb e u sed i n n e tw o rk s co n t a in in g h u n d red s o f t h o u san d s o fp r o c e s s or s . T h a t w o u l d b e a B I G n e t w o r k !

Th e o p era t i n g sy s t em INM OS su p p l i ed fo r t h e T ran s -p u t e r was ca l l ed ' o ccam' [7 ] , wr i t t en b y Dav id M ay [8 ]an d n amed a f t e r t h e En g l i sh p h i l o so p h er Wi l l i am o f Oc-cam (1 3 0 0 -1 3 4 9 ) . O ccam was d es ig n ed t o eas i ly d esc r i b ec o n c u r r e n t p ro c e s s e s w h i c h c o m m u n i c a t e v i a o n e - w a ych an n e l s . Th e ' p ro cess ' i s t h e es sen t i a l o p era ti o n i n o c -cam, wi th fo u r su b ty p es : ' a s s i g n m en t ' , ' i n p u t ' , ' o u tp u t 'an d 'w a i t ' . Th e se su b ty p es co u ld b e u sed t o co n s t ru c t

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m o r e c o m p l e x p r o c e s s e s f o r s e q u e n t i a l o r p a r a ll e l e x e c u -t i o n, wh ich co u ld u se i n p u ts f ro m o th er CP U s . Co n d i -t i o n a l ex ecu t i o n was su p p o r t ed . A r ev i sed v e r s io n , ' o c -cam 2 ' , ad d e d f l o a t i n g -p o in t ma th an d d a t a t y p in g [9 ] .

W e l l , h a v i n g s u c h a p o w e r f u l s t a c k - o r i e n t e d C P U a th an d , h o w lo n g d o y o u t h in k F o r th en th u s i as ts an d F o r thl an g u ag e su p p l i e r s co u ld r es i s t wr i t i n g a su i t ab l e F o r thfo r t h e T ran sp u t e r? An sw er : n o t v e ry l o n g a t a ll . On eTran sp u t e r en th u s i as t [ 1 0] h as l i s t ed a n u m b er o f p ro -g r a m m i n g l a n g u a g e s w h i c h h a v e b e e n i m p l e m e n t e d o nTran sp u t e r n e two rk s ; s ev era l F o r th s a r e i n c lu d ed , so meo f w h i c h a r e m e n t i o n e d b e l ow .

Th e f ir s t i s ' I n m o s T ran s p u t e r F o r th ' , w h i ch i s fo u n d i nth e p a ra l l e l co mp u t in g a r ch iv e a t t h e Un iv er s i t y o f Ken ti n En g l an d [ 1 1 ] . Th e l i s ti n g s g iv en co v er F o r th s f ro m th e1 6 -b it T -21 2 t o t h e 3 2 -b i t T -8 0 0 T ran sp u t e r s . Th e n e c-es sa ry h a rd ware i s d esc r i b ed , F o r th imag es an d a l o ad eri s p ro v id ed , an d i n s t ru c t i o n s o n r eb u i l d in g t h e F o r th s fo ro th er co n f ig u ra t i o n s a r e g iv en .

Ne x t i s a F o r th -7 9 fo r t h e T ran sp u t e r . No e l Hen s o n[1 2 ] , a fo rmer t eam l ead er a t Co g en t R esearch , d es ig n eda d e s k t o p c o m p u t e r u s i n g 3 2 I N M O S T - 4 1 4 a n d T - 8 0 0p ro cesso r s . He r ep o r t e d i n a p o s t i n g t o co m p . l an g . fo r t ho n M ay 4 , 1 9 9 8 t h a t t h e o n ly q u i ck way t o d eb u g t h eh ard ware was t o u se F o r th . Co n s eq u en t l y h e an d hi st eam wro t e a F o r th -7 9 fo r t h i s h a rd ware , wh ich ex e-cu t ed q u i ck ly o n t h e T ran sp u t e r an d wh ich co u ld r ep l i -c a t e i ts e l f f r o m n o d e t o n o d e . T h e p r o g r a m f i l e s a r c h iv e di n ' r o m . z i p ' c a n b e d o w n l o a d e d t h r o u g h l i n k s a t M r .M e e n a k s h i s u n d a r a m ' s w e b s i te .

Nex t i s 'Tu rb o -F o r th 8 3 ' f o r t h e 3 2 -b i t TS 0 x Tran s -p u t e r s . Th e p ro g ra m f i le s a r ch iv ed i n ' f - t p -1 0 0 .z ip ' canb e d o wn lo ad ed t h ro u g h t h e ab o v e web s i t e l i n k s . F in a l l yt h e re i s ' t F o r t h P a r a ll e l F o r t h v l . 0 ' b y T h e D u t c h F o r t h

W o r k s h o p , a c c e s s i b l e v i a t h e a b o v e w e b s i t e o r d i r e c t l y[1 3 ]. Th i s t r an sp u t e r F o r th co n t a in s an i n t eg ra t ed o p ti -miz er an d an as semb le r ; i t r u n s ab o u t h a l f a s f as t a s h an d -o p t i m i z e d a s s e m b l e r b u t m u c h f a s te r t h a n T r a n s p u t e r Cco d e . I t i s AN S -co m p l i an t . Th e I /O o f tF o r th is h an d l edwi th a se rv er wr i t t en i n t h e C l an g u ag e an d i s cu r r en t l ya v a il a b le f o r M S - D O S a n d U N I X m a c h i n e s .

T h e a b o v e T r a n s p u t e r F o r t h s m a y b e s a t i s f a c t o r y f o rg en era l u se , b u t I h av e n o t h ad an y p er so n a l ex p er i en cewi th th em. M y sa in t ed g ran d mo th er a lway s u sed t o say ," I f y o u d o n ' t k n o w d i a m o n d s , k n o w y o u r j e w e l e r " . T os t r e t ch a metap h o r a b i t , l e t m e r ep h rase t h a t w i sd o m : " I fy o u d o n ' t k n o w F o r t h, k n o w y o u r F o r th s o u rc e " . O n eF o r t h v e n d o r I k n o w q u i t e w e l l w h o o f f e r s T r a n s p u t e rF o r t h i s M i c r o P r o c e s s o r E n g i n e e r i n g L t d o f S o u t h a m p -

to n , En g l an d . Th ey se l l a P C-b ased o r Un ix -b ased F o r thc r o s s - c o m p i l e r f o r t h e T 2 x x , T 4 x x a n d T 8 x x C P U s [ 14 ].

Th e ab o v e l i st is u n d o u b ted ly i n co m p le t e . Be su re t och ec k t h e r e l ev an t n ewsg ro u p s [ 1 5 -1 7 ] , t h e In t e rn e t P ara l-l e l Co m p u t in g A rch iv e [ 1 1 ] , t h e Ox fo rd Un iv er s i t y T ran s -p u t e r A r c h i v e [ 1 8 ] a n d t r y k e y w o r d s e a r c h e s w i t h y o u rf av o r i t e sea rch en g in es . By t h e way , t h e T ran sp u t e r wasp i c k e d u p c o m m e r c i a l l y f r o m I N M O S b y S T M i c r o e l e c -t r o n ic s ( fo r m e r l y S G S - T h o m s o n ) [ 19 ] . P l e a s e c o n t a c tt h em fo r p r i c i n g an d av a i l ab i l it y .

F in a l l y i n t h is sec t i o n , l e t me m en t io n t h e u se o f F o r thwi th t h e l eg en d ary M ass iv e ly P ara l l e l P ro cesso r (M P P )d e v e l o p e d by D r . J o h n D o r b a n d , N A S A / G o d d a r d S p a c eF l i g h t C e n t e r in t he m i d - 1 9 8 0 ' s [ 2 0 ] . T h e M P P c o n -s i s t ed o f 1 6 ,0 0 0 i n d iv id u a l s i n g l e - i n s t ru c t i o n mu l t i p l e -d a t a (S IM D) p ro cesso r s , a r r an g ed in c lu s t e rs . Eac h o ft h ese was f ed b y i ts o wn in s t ru c t i o n s tr eam. Co m mu n i -c a t i on b e t w e e n c l u s te r s o f p r o c e s s o r s w a s a c c o m p l i s h e db o th ex p l i c i t l y an d imp l i c i t ly . Th e M P P was u sed fo r im-a g e e n h a n c e m e n t f r o m s p a c e c r a f t a n d t h e H u b b l e T e l e -sco p e , co m p lex g rap h i cs o p era t i o n s , s imu la t i o n o f ce l lu -l a r au to mata , f i n i t e e l em en t an a ly s i s an d so lu t i o n o f o th e ram az in g ly co m p lex p ro b l ems . I t is u n l i k e ly th a t y o u o r Iwi l l ev er g e t o u r h an d s o n su ch a v as t p a ra l le l co mp u te r ,b u t i f I d id I wo u ld u se i t t o an a ly ze D NA s t ru c tu re , p ro -t e i n s y nt h e s is a n d e n z y m e b i n di n g s i te d y n a m i c s . W h a tw o u l d y o u u s e i t f o r ?

D o r b a n d h a s w o r k e d o n a n u m b e r o f o t h e r p a r a l l e lc o m p u t e r s . H e h a s b e e n a m e m b e r o f t h e A N S F o r t hS t a n d a rd s C o m m i t t e e , w h i c h p r o v e s t h at h e k n o w s a g o o dth in g wh e n h e sees i t.

4 L a t e s t P a r a l l e l F o r t h D e v e l o p -m e n t s

S o m e o f t h e p r e c e e d i n g i n f o rm a t i o n p e r t a in s t o t h e u s eo f F o r th o n an c i en t o r u n o b t a in a b l e h a rd ware . No w l e t ' sl o o k a t cu r r en t ev en t s wi th Je f f F o x , a l o n g - t im e F o r then th u s i as t , h a rd ware / so f tw are d es ig n er an d p ara l le l co m-p u t i n g wiza rd [2 1 ] . J e f f h as wo rk ed wi th F o r th c r ea to rC h u c k M o o r e f o r a d e c a d e , i n c l u d i n g s e v e r a l F o r t h - i n -s i l icon pro jects .

F o x h a s l o o k e d lo n g a n d h a r d a t m a r r y i n g F o r th w i t hL I N D A , w h i c h i s n o t a p r o g r a m m i n g l a n g u a g e b u t away o f ex t en d in g co n v en t i o n a l l an g u ag es i n to t h e p a ra l -l e l p r o c e s s in g a r e n a ( ie : F O R T R A N - L I N D A , C - L I N D A ,F O R T H - L I N D A ) [ 2 2 ]. T h e L I N D A p a r ad i g m is b a se do n ac t i v e an d p ass iv e ' t u p l es ' . A t u p l e is a seq u en ce o f

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t y p e d f i e ld s e a c h o f w h ic h h a v e (o r c a n h a v e ) a v a lu e . T u -p le s e x i s t i n ' t u p le s p a c e ' , w h ic h i s a g lo b a l , a s s o c ia t iv e ,o b j e c t m e m o r y . I t c a n b e i m p l e m e n t e d o n m u l t i p r o c e s -s o r sy s t e m s o r c o m p u t e r n e t w o r k s . A n a c t i v e t u p le s u p -p o r t s p ro c e s s e s w h ic h a re e x e c u t in g ; p a s s iv e tu p le s e x -c h a n g e in fo rm a t io n ( l ik e ' P o s t - I t ' n o te s ) . A c t iv e tu p le sc a n s p a w n s im u l t a n e o u s ' c h i ld ' p ro c e s s e s in o th e r t u p le sa s n e e d e d to p e r f o rm c a lc u la t io n s in p a ra l le l ; p a s s iv e tu -p l e s s y n c h r o n i z e t h e s e p r o c e s s e s a n d m o v e d a t a a r o u n d .

I n F O R T H - L I N D A , t h e m a s t e r p r o ce s so r m a n a g e s t h en e tw o rk , b re a k s u p l a rg e p ro b le m s in to s m a l l e r p a r t s a n dm a n a g e s t h e a c t i v e ' w o r k e r t u p l e s ' w h i c h p e r f o r m t h en e c e s s a ry c a l c u la t io n s in p a ra l l e l . W h e n a w o rk e r tu p lef in i s h es i t s c u r re n t t a s k , i t i s r e c y c le d a n d r e a s s ig n e d to an e w t a s k . T h e n u m b e r o f a v a i l a b l e p r o c e s s o r s i n t he n e t -w o r k i s i r r el e v a nt : t h e m o r e C P U s w h i c h a r e a v a i l a b l e t oru n a c t iv e tu p le s , th e f a s t e r t h e p ro b le m c a n b e s o lv e d .

T h e m a s t e r p r o c e s s o r l o a d s a c o p y o f F o r t h i n to e a c ha v a i l a b le p ro c e s s o r . A t t h e lo w e s t le v e l , t h e s e F o r thp r o c e s s o r s e x e c u t e F o r t h c o d e p r e t t y m u c h i n a n o r -m a l f a s h io n , w i th th e u s u a l s t a c k o p e ra t io n s b e in g lo c a lto th e p ro c e s s o r . A t a h ig h e r l e v e l , L I N D A e x te n s io nw o r d s t o F o r t h c a n b e e x e c u t e d b y t h e s e s a m e p r o c e s -s o r s , r e a d in g o r w r i t i n g d a ta a n d /o r m e s s a g e s in p a s s iv et u p le s . F O R T H - L I N D A h a s i n h e r en t l o a d ba l a n c in g . T h eM o n tv e t i s h s k y p a p e r d e s c r ib e s a l l t h i s i n g re a t d e t a i l a n di t is b e a u t i fu l t o r e a d a n d u n d e r s t a n d .

O b v i o u s l y , a n y n e t w o r k e d c o m p u t e r s y s t e m w h i c hc o u l d r u n F o r t h c o u l d s u p p o r t F O R T H - L I N D A , f r o m t h a tl i t t l e 8 0 3 1 -b a s e d h y p e rc u b e , t o th e T ra n s p u te r s , t o t h eMP P . B u t J e f f F o x h a s a c u te l it t le C P U fo r u s w h ic hfu r th e r e n h a n c e s th e b e a u ty o f t h is a p p ro a c h : a F o r th e n -g in e k n o w n a s th e ' F 2 1 ' [2 3 ] . T h e F 2 1 i s a s t a n d -a lo n e2 0 - b i t F o r t h p r o c e s s o r w h i c h c a n b e n e t w o r k e d i n ri n g s ,g r id s , m u l t i d i m e n s i o n a l a r r a y s o r o t h e r n e t w o r k t o p o l o -g i e s a s n e e d e d t o s u p p o r t v a r i o u s t y p e s o f p r o b l e m s . A sa s t a n d - a l o n e C P U i t c o n t a i n s a n a l o g A / D - D / A , p a r a l -l e l p o r t s , a r e a l t im e c lo c k , a v id e o c o p ro c e s s o r fo r g e n -e r a ti n g T V - t y p e s y n c h r o n i z e d N T S C o r R G B c o l o r d i s-p l ay s , a m e m o r y c o n tr o l le r ( S R A M / D R A M / R O M ) a n dh i g h - s p e e d D M A - s u p e r v i s e d s e r i a l I / O f o r n e tw o r k i n g . AC P U c y c l e i s 2 0 n se c .

W h y i s t h e F 2 1 a 2 0 -b i t p ro c e s s o r? E s s e n t i a l ly , b e -c a u s e th i s i s a ll i t n e ed s . E a c h o f t h e C P U ' s 2 7 in -s t ru c t io n s i s 5 -b i t s l o n g , a l lo w in g fo u r in s t ru c t io n s to b ef e t c h ed p e r m e m o r y c y c l e a n d e x e c u t e d s i m u l ta n e o u s ly .A m a x i m u m s u s t a i n e d r at e o f 2 0 0 M I P S e x e c u t i n g o u t o fS R A M c a n b e a c h i e v e d i n t h i s f a s h i o n ( R O M i s f a s t e r ,D R A M s l o w e r ) . J e f f F o x o f f e r s a f r e e F 2 1 s o f t w a r e s i m -u l a t o r a n d e m u l a t o r w h i c h y o u c a n d o w n l o a d f r o m h i s

w e b s i t e . T h e F 2 1 c h ip i s n o w u p to r e v i sio n ' d ' a n d i sp a c k a g e d in a 6 8 -p in P L C C . P le a s e c o n ta c t J e f f a t U l t r aT e c h n o lo g y fo r p r i c in g a n d a v a i l a b i l i t y .

F o x a n d M o n t v e l i s h s k y w o r k e d t o g e t h e r o n ' F * F ' ,t h e i r F or t h - d is t i ll e d v e r s i o n o f L I N D A f o r th e F 2 1 . T h eo r i g i n a l F O R T H - L I N D A i m p l e m e n t a t i o n r e q u i r e d f i v eF o r th w o rd s to a c c o m p l i s h th i s ; t h e n e w F *F re q u i re so n ly tw o , c a p i t a l i z in g o n th e b u i l t - i n c o m m u n ic a t io n sh a rd w a re s u p p o r t o f t h e F 2 1 w h e n u s e d in n e tw o rk s .T h e p a s s i v e t u pl e m o d e l h a s b e e n r e m o v e d f r o m L I N D A ,v a s t l y s i m p l i f y i n g d a t a c o m m u n i c a t i o n s a n d m e s s a g e -p a s s in g b e tw e e n a c t iv e p ro c e s s e s . A n y F 2 1 c a n s e n d d a tato a s in g le n o d e , g ro u p s o f n o d e s o r t o th e e n t i r e n e tw o rk ;th e F o r th w o rd ' G ! ' s to re s d a t a to th e s e g lo b a l d a t a s t~ c -tu re s . R e a d in g g lo b a l v a r i a b le s o r d a t a s t ru c tu res w o rkl ik e lo ca l m e m o ry f e t c h e s a n d a re q u i t e fa s t. T h e F o r thw o r d ' R X ' s e ts u p a F o r th w o r d e x e c u t i o n s t r ea m f o rt r a n s m is s io n to a n d ru n n in g o n o th e r n o d e s . T h i s F *Fs o f t w a r e c o u l d b e r u n o n o t h e r h a r d w a r e i f y o u ' d l i k e toh o m e b r e w a f e w b o a r d s w i t h y o u r f a v o ri t e C P U a n d s o m eg lu e lo g ic ; h o w e v e r , t h e F 2 1 s e e m s to b e th e id e a l s e tu pfo r F ' F , e s p e c ia l ly s in c e i t s i n s t ru c t io n s e t i s t ru ly m a d efo r F o r th .

5 C o nc l us io nT h i s l o n g - w i n d e d o d y s s e y h a s g o n e b a c k w a r d a n d f o r -w a rd in t im e , l o o k e d a t s e r i a l a n d p a ra l l e l C P U s , s in g lya n d b y th e h u n d re d s o f t h o u s a n d s , a n d h a rd w a re a n d s o f t -w a r e c o n s id e ra t io n s fo r p a ra l l e l p ro c e s s in g . T h e g o o dn e w s i s : b y n o w , y o u r u n d e r s t a n d in g o f p a ra l l e l p ro c e s s -in g a n d th e ro l e o f F o r th h a rd w a re a n d s o f tw a re in i t i sc o n s id e ra b ly g re a t er . T h e b a d n e w s i s: w e h a v e b a re lys c ra t c h e d th e s u r fa c e o f th i s t o p ic ! I i n v i te y o u to lo o km o re d e e p ly i f y o u h a v e a n in t e re s t i n th i s a re a , o r b e t te rs t il l h a v e a p ro p o s e d a p p l i c a t io n . C o n ta c t t h e p e o p le a n dre s o u rc e s I h a v e o u t l in e d fo r y o u . G e t i n v o lv e d !

S o t h e r e y o u h a v e i t: w h e n y o u s p e a k o f p a ra l l el c o m -p u t in g s y s t e m s , d o n ' t fo rg e t t o th in k o f F o r th .

6 Bib l io g ra phy1 . h t t p : / / e i . c s . v t . e d u / ~ h i s t o r y / V o n N e u m a n n . h t m l .

2 . H o w l a n d , J o h n , " L e c t u r e N o t e s f o r C S C I3 0 1 : G r e a t I d e a s i n C o m p u t e r S c i e n c e ", D e p t C o m pS c i , T r in i ty U n iv , S a n A n to n io , T X , 1 99 5 . h t tp : //w w w . c s . t r i n i t y . e d u / A b o u t / T h e _ C o u r s e s / c s 3 0 1 / 1 2 . p a r -a l l e l . p ro c e s s in g / 1 2 . p a ra l l e l . p ro c . h tm l .

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