CPE319 LECTURE NOTES
WINTER 1998
PART THREE
INTRODUCTION
TO DIGITAL DESIGN IN THE 21ST CENTURY - A PERSPECTIVE!
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Digital Design in the 19th century
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Technology: gears, cams, cogs, and other mechanical parts
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Feasibility: none really worked except Babagge's first machine
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People: Pascal, Babbage, et. al.
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Digital Design in the 20th century
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1900-1950+: Electromagnetic relays
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Very slow
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Very expensive
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Not very reliable (they got "sticky")
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Still actual machines were built, some by I.B.M.
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Minimum cost design introduced.
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Cost = K1V+K2L V=# of Variables (fixed) and L=# of
literals. Minimize L for least cost.
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Quine and McCluscky develop tabular reduction
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Karnaugh develops map method
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1950+ to 1960+: Vacuum tubes
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Faster
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Expensive
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Not very reliable (burned out)
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EINAC the first Vacuum Tube Computer (in USA), followed by UNIVAC, firs
commercial computer, circa 1951.
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Minimum cost procedures - I don't remember!
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1960+ to 1970-: Transistors
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Still faster
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Less Expensive (especially in terms of power needed)
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Quite reliable (as soon as good transistors were available)
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Early computers: IBM 7090, IBM1620, UNIVAC Missile Guidance Computers.
DEC PDP8 first successful minicomputer using transistor technology
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Minium cost procedures _ I don't remember!
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1970- to 1980+: SSI and (later) MSI
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Somewhat faster (faster transistors)
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Considerably less expensive
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Even more reliable (less solder joints)
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Many computer using this technology, many of them minicomputers. HP2100
series used early IC's as did the DEC PDP8I.
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Minimum Cost procedures
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Cost = K(2P+L) where P=# of product terms and L= # of literals. Twice as
inportant to reduce product terms as to reduce literals. This relation
comes from the observed fact that SSI costs are essentially dependant on
the number of pins in the DIP.
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Since reducing L to a minimum has to reduce P as well, Relay design techniques
were still applied!
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1980+ to 1990+: MSI and PLD's
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Somewhat faster since PLD's use less levels of logic that SSI gates
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Somewhat less expensive since fewer IC's needed
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Somewhat more reliable (less IC's)
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By now computers using microchips. Digital design used for special purpose
digital functions.
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Minimum cost procedures change dramatically. If the design fits in the
desired PLD, all implementations cost the same (same IC!). Only consideration
is the number of product terms. Number of literals immaterial.
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Hardware Design/Description Languages (HDL) come into being since some
sort of software is required to "burn" the PLD. As time goes by, the software
becomes more sophisticated doing more than simply producing a JEDEC Fuse
file.
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1990+ to 2000 (end of 20th century): CPLD's and FPGA's and etc.
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Still faster since delays inside a CPLD or FPGA are considerably less than
between chips.
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Probable less expansive, but who knows? Who cares?
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Still more reliable (one or only a few IC's for the entire system
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Used for special purpose functions. Could be used to fabricate a microprocessor,
but probably not.
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With the rapid change in technology, fabrication costs are often not the
critical factor. Often it is more important to get the product on the market
fast (before the competition). Synthesis costs very difficult to
estimate. Not necessary anyway. See NOTES07!
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HDL becomes more sophisticated. Several HDL's become standard, VHDL and
Verilog being the most common. Digital design becomes much more abstract
(i.e., we don't look at the individual logic gates and flip-flops anymore
(not very much, anyway).
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The 21st century. By the time you get an engineering design
job, the 21st century will be here (or almost here). Digital
design in the 21st century will be radically different, relying
more and more heavily on HDL's and design software. To be ready, you need
to know one (or more) HDL reasonably well. So there's the goal of this
class.
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