1.4. THE POWER OF COMPUTERS: SPEED NOT SMARTS!Blazing SpeedComputers need not be smart as long as they are fast. The code breaking we described in Section 1.2 could have been done by humans, but it would have taken too long for the result to be useful. Credit cards are probably the most visible effect of computers in everyday life. It could take a person several minutes to record a card transaction at the central office and that would limit the use of cards severely. With a computer the central office transaction can be completed in a fraction of a second. Early computers (in the 1940's) could perform around several thousands of machine operations per second. Today, your ordinary laptop or desktop can perform several billions of machine operations per second. define Of course, most humanly understood computations require several machine operations, so they tend to be a bit slower. For example, the 1948 IBM SSEC machine performed "only" 50 multiplications per second. Eventually, technological developments led not only to increase in the basic speed but also the more efficient implementation of more complex operations. The VAX machines built by Digital Equipment Corporation (DEC) and introduced around 1980 had a speed of one million operations per second. My desktop Dell computer (vintage 2002) has a 1.8 GigaHerz (1.8 billion clock ticks/second) Pentium processor that can execute about three instructions per clock tick, so its speed is about 5 billion machine operations per second. The table below shows the speed for specific operations.
Recall (from Section 1.2) that there are 3X107 seconds in a year and a human would need more than a second per multiplication. To match the amount of multiplications that my desktop can do in a second I would have to spend more than (109)/ (3X107) years or over 30 years. Moore's LawComputer memory has also been increasing, even faster than speed. Gordon Moore, one of the founders of Intel, wrote in 1966 that the number of transistors that could be packed in given size of silicon would double every two years. The prediction proved accurate and it is has been called Moore's law. Increasing the local memory (RAM for Random Access Memory) of a computer also contributes to increasing its speed. Table 1.4.1 that accessing the hard drive is very slow compared to other operations. My desktop has 768 Megabytes of RAM while the first personal computers thirty years ago had only 64 Kilobytes, so we have seen an increase in RAM size of about 10,000 in 30 years. While reading from the hard drive is slower than reading from the RAM, it is still much faster than reading from tapes or compact disks. And hard drives have also benefited form Moore's Law. The following table shows the increase in hard drive capacity for the last 30 years. For comparison, we give the number of pictures and pages of text that could be stored on such a drive. For pictures we assume one produced with a good digital camera (even though such cameras did not exist in 1980). Such pictures require about one Megabyte each. For books we assume a 500 page hardcover. Each page contains about 2,000 characters or 2 thousand bytes so the whole book would require about one Megabyte. We may note in passing that a 500 page book contains over 100,000 words so the proverbial "a picture is worth a 1000 words" is an understatement.
My desktop machine whose speed is described in Table 1.4.1 has a 37.2 Gigabyte hard drive that is about 50 times the size of its RAM. about image processing We conclude this section with a table of important events in Computer history.
Speed and MischiefOnce we have a fast way to do simple things all sorts of possibilities open, including searching for information but also invasion of privacy. We will examine these issues in Chapter 2 and, especially, in the section on Data Mining. | |||||||||||||||||||||||||||||||||||||||||||||||||||||