Information Technology Reference
In-Depth Information
1981
1996
2011
factor
MIPS
1
300
10000
10K
MIPS/$
$100K
$30
$0.50
200K
DRAM
128KB
128MB
10GB
100K
Disk
10MB
4GB
1TB
100K
Home
Inter-
256
Kbps
9.6 Kbps
5 Mbps
500
net
LAN
network
3 Mbps
(shared)
10 Mbps
1 Gbps
300
Users per
machine
100
1
<< 1
100+
Figure1.10: Computer performance over time
10. For the computer you are currently using, how should the operating system
designers prioritize among reliability, security, portability, performance,
and adoption? Explain why.
1.3
A brief history of operating systems
We conclude this chapter with a discussion of the origins of operating systems,
as a way of illustrating where operating systems are headed in the future. As
the lowest layer of software running on top of computer hardware, operating
systems have been around nearly as long as the first computers, and they have
evolved nearly as rapidly as computer hardware.
1.3.1
Impact of technology trends on operating systems
The most striking aspect of the last fifty years in computing technology has
been the cumulative eect of Moore's Law, and the comparable advances in
related technologies such as memory and disk storage. Moore's Law states
that transistor density increases exponentially over time; similar exponential
improvements have occurred in many other component technologies. Figure 1.10
provides an overview of the past thirty years of technology improvements in
computer hardware. The cost of processing has decreased by over five orders of
magnitude over the past thirty years; the cost of memory and disk capacity has
followed a similar trajectory. Of course, not all technologies have improved at
the same rate; disk latency has improved over time, but at a much slower rate
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