This note summarizes the discussion for the benefit of those who may wish to trace the development of thought on this subject

Hosier, W. A.

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Memorandum M-14.57 Page 1 of 2 Digi tal Computer Laboratory Massachusetts I n s t i t u t e of Technology Cambridge, Massachusetts CUSSfFfCATiOM CHAAGtD *C-Datt: ^.rirrkA SUBJECT: WWII BLOCK DIAGRAMS MEETING OF APRIL 1 0 . 1952 T o : F r o m : • ^ ^ A D . UtV. 6 w. A.wg^QUJViENT ROO^l f A b s t r a c t : This who i riepprt summarizes the d i sc t t s s ld i Cor maw- wish: to t r a c e th$ deyaldpiceiit af the b e n e f i t of those \hought on t h i s sub jec t . P r e s e n t : D. R. Brown G. R. Griggs S. h . Dodd R. R. Bvere t t J . W. Borreste E . R. J . GJrosch W. A. Hosier , R . , C . J e f f r * * 1 ^ I H F0>J a c p?8^ J •'• Br M R. P . Mayer W. Ogden I . Reed N. H. Taylor N. T a y l o r remarked i n opening t h i s meeting t h a t h e , J e f f r ey , and Reed had been d i scuss ing the genera l problem of symbolic l o g i c a l ana lys i s of computer components by methods set fo r th i n J e f f r e y ' s r e p o r t E-458. Although not ag ree ing to p a r t of the group' s working f u l l time in t h i s d i r e c t i o n , Mr. F o r r e s t e r conceded that i t would be a good idea to subject opera t ions and components to such analysis from time to t ime , as they come up in the g roup ' s d i s c u s s i o n s . Mr. Tay lo r also c a l l e d a t ten t ion t o the exposi t ion of the a i r defense problem t o be given by R. Walquist a t the WWII meeting Apr i l 1 1 . The major part of t h i s meeting was given over to an exposi t ion and discussion of the "s ingle r e g i s t e r " computer by R. Mayer and J . For-r e s t e r . Their conception of such a mechine i s se t for th i n d e t a i l , with t r a f f i c diagrams of the p r i n c i p a l orders , i n Mayer's r epo r t E-459. By " s i n g l e r e g i s t e r " , they mean " s i n g l e f l i p - f l o p r e g i s t e r " or " s i n g l e vacuum-tube r e g i s t e r " i n t h i s case , s ince a l l modif ica t ions d i s -cussed did have o ther " r e g i s t e r s " (e .g. Program Counter, Accumulator, S h i f t Counter) which were no th ing more than spec ia l r e g i s t e r s of the magnet ic memory, se lectable by the control switch without going through t h e storage s w i t c h . s ^ \ Both modificet ions discussed inco memory (switching time assumed 2 microseconds' and rewrite (Mr. 1 MTUWYFrt SECURITY INFORMATION ed the same magnetic with destructive readout similar discussion a APPROVED FOR PUBLIC RELEASE. CASE 06-1104.Memorandum M-1457 \ ^ * P a 8 e 2 r o f a machine w i t h non-des t ruc t ive readout) . Also , both were d is t inguished b y introducing a s storage s e l e c t i o n matrix a switch of the type proposed b y K. Olsen ( s e e M-1282), t he e s s e n t i a l v i r t u e of which i s t h a t once se t u p f o r read-out by the f l i p - f l o p of the s to rage switch, r e w r i t i n g (or r ead-i n of a new word t o the s e l e c t e d address) can be accomplished with a s ing le p u l s e to the s e l e c t e d memory r e g i s t e r at l e i s u r e , a f te r the f l i p - f l o p i s c l e a r e d or r e - s e t . Final ly , b o t h made use of magnetic s tepping r e g i s t e r s t o do the a c t u a l issuing of command pulsesj t he se r e g i s t e r s , once t r iggered b y t h e control s w i t c h , au tomat ica l ly maintain the sequence of command p u l s e s and complete the order without fu r the r need for the cont ro l switch. The two modifications differed mainly in that one had a separate f l i p - f l o p r e g i s t e r for i t s " s e l e c t i o n r e g i s t e r " (combination of control s w i t c h and s t o r a g e switch); t h e other had a common f l i p - f l o p r e g i s t e r b o t h for s e l e c t i o n and for a r i t h m e t i c o p e r a t i o n s , making use of a gate g e n e r a t o r or p u l s e s t retcher t o s tore an i n s t r u c t i o n b r i e f l y between f l i p -f l o p and s e l e c t i o n matrix end t h u s free the f l i p - f l o p for e a r l i e r c l ea r ing . W i t h a clock-pulse ra te of 1 megacycle, the operat ions ca and ts. require 1 2 and 13 microseconds, r e s p e c t i v e l y , in both systems; "mul t ip ly" becomes q u i t e lengthy and probably j u s t i f i e s add i t i ona l equipment. I t was pointed out t h a t the delay introduced by the pulse s t r e t c h e r i n t h e second machine could e q u a l l y well have been placed on the read-out s i d e of the memory. Two o r t h ree other ques t ions were r a i s e d at the end of the meeting: I . Reed proposed, a s an i l l u s t r a t i o n of the a p p l i c a t i o n of Boolean m e t h o d s (symbolic logic) to computer design, t h a t a ccmputer could be b u i l t u s i n g only 4 o r d e r s : " s u b t r a c t " , " transfer t o control" (analogous to cp. o r J J E ) , " t r ans f e r back to memory and shif t r i g h t " , and " h a l t " . I t was sugges t ed that h e present t h i s i n greater d e t a i l . H. Grosch suggested a survey of what might be ca l l ed "clever a r i t h m e t i c t e c h n i q u e s " such a s t h e mu l t i p l i ca t ion method used in some mach ines and known as " c r i s s - c r o s s " ; fu r the r , t h a t a s tudent might p r o f i t -a b l y be assigned such a survey a s a thesis s u b j e c t . N. T a y l o r pointed ou t t h a t two or more r e l a t i v e l y simple r e g i s t e r s m i g h t be p r o f i t a b l y subst i tu ted for one e l a b o r a t e "universal r e g i s t e r " i n s o m e cases. y V ^ V w« A - Hosier WAH/cp C A < APPROVED FOR PUBLIC RELEASE. CASE 06-1104.

WWII Block Diagrams Meeting of April 10, 1952

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WWII Block Diagrams Meeting of April 10, 1952

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