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CHAPTER 1-4
EXAMPLE COMPUTER FAMILIES
Introduction to the x86 architecture
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In 1968, Robert Noyce (inventor of the silicon integrated circuit), Gordon Moore (of Moore's law
fame), and Arthur Rock (a San Francisco venture capitalist), formed the Intel Corporation to make
memory chips.
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------------------------------------------------------------------------------------- ------------------------------------------Figure 1-11. Key members of the Intel CPU family. Clock speeds are measured in MHz (megahertz),
where 1 MHz is 1 million cycles/sec.
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All the Intel chips are backward compatible with their predecessors back as far as the 8086.
o In other words, a Pentium 4 or Core can run 8086 programs without modification. Of course, the
Core is many times more complex than the 8086, so it can do things that the 8086 cannot.
o This compatibility has always been a design requirement for Intel.
o These piecemeal extensions have resulted in an architecture that is not elegant.
It is interesting to note that although Moore's law has long been associated with the number of bits in a
memory, it applies equally well to CPU chips.
While Moore's law will probably continue to hold for some years to come, another problem is starting
to overshadow it: heat dissipation.
o Smaller transistors make it possible to run at higher clock frequencies, which requires using a
higher voltage.
o Power consumed and heat dissipated is proportional to the square of the voltage, so going faster
means having more heat to get rid of.
o At 3.6 GHz, the Pentium 4 consumes 115 watts of power. That means it gets about as hot as a
100-watt light bulb. Speeding up the clock makes the problem worse.
o In November 2004, Intel canceled the 4GHz Pentium 4 due to problems dissipating the heat.
As a consequence, the once-relentless march of the clock may be temporarily stymied, at least until
Intel's engineers figure out how to get rid of all the heat generated in an efficient way.
o Instead, Intel's future plans call for putting 2 CPUs on a single chip, along with large shared cache.
o Taking advantage of these multiprocessors poses great challenges to programmers, because
multiprocessors require the programmer to explicitly orchestrate parallel execution using threads,
semaphores, shared memory and other headache- and bug-inducing technologies.
Metric units
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----------------------------------------------------------------------------------------------------------------------------- --Figure 1-16. The principal metric prefixes.
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The prefixes are typically abbreviated by their first letters, with units greater than 1 capitalized (KB,
MB, msec, nsec, etc).
o One exception for historical reason is kbps for kilobits/sec.
o Since milli and micro both start with m, a choice had to be made. Normally, "m" is for milli and
"" is for micro.
For measuring memory and file sizes, kilo means 2 10 rather than 103, because memory is always a
power of 2.
o Thus, a 1 KB memory contains 1024 bytes, not 1000 bytes.
o Similarly, 1MB memory contains 220 (1,048,576) bytes, 1GB memory contains 230 (1,073,741,824)
bytes, 1TB memory contains 240 (1,099,511,627,776) bytes.
o However, a 1-kbps communication line can transmit 1,000 bits/sec and a 10-Mbps line can
transmit 10,000,000 bits/sec because these speeds are not powers of 2.