Hardware Reference
In-Depth Information
PROBLEMS
1.
Consider the operation of a machine with the data path of Fig. 2-2. Suppose that load-
ing the ALU input registers takes 5 nsec, running the ALU takes 10 nsec, and storing
the result back in the register scratchpad takes 5 nsec. What is the maximum number
of MIPS this machine is capable of in the absence of pipelining?
2.
What is the purpose of step 2 in the list of Sec. 2.1.2? What would happen if this step
were omitted?
3.
On computer 1, all instructions take 10 nsec to execute. On computer 2, they all take 5
nsec to execute. Can you say for certain that computer 2 is faster? Discuss.
4.
Imagine you are designing a single-chip computer for an embedded system. The chip
is going to have all its memory on chip and running at the same speed as the CPU with
no access penalty. Examine each of the principles discussed in Sec. 2.1.4 and tell
whether they are so important (assuming that high performance is still desired).
5.
To compete with the newly invented printing press, a medieval monastery decided to
mass-produce handwritten paperback topics by assembling a vast number of scribes in
a huge hall. The head monk would then call out the first word of the topic to be pro-
duced and all the scribes would copy it down. Then the head monk would call out the
second word and all the scribes would copy it down. This process was repeated until
the entire book had been read aloud and copied. Which of the parallel processor sys-
tems discussed in Sec. 2.1.6 does this system resemble most closely?
6.
As one goes down the five-level memory hierarchy discussed in the text, the access
time increases. Make a reasonable guess about the ratio of the access time of optical
disk to that of register memory. Assume that the disk is already online.
7.
Sociologists can get three possible answers to a typical survey question such as ''Do
you believe in the tooth fairy?''—namely, yes, no, and no opinion. With this in mind,
the Sociomagnetic Computer Company has decided to build a computer to process sur-
vey data. This computer has a trinary memory—that is, each byte (tryte?) consists of 8
trits, with a trit holding a 0, 1, or 2. How many trits are needed to hold a 6-bit number?
Give an expression for the number of trits needed to hold
n
bits.
8.
Compute the data rate of the human eye using the following information. The visual
field consists of about 10
6
elements (pixels). Each pixel can be reduced to a superposi-
tion of the three primary colors, each of which has 64 intensities. The time resolution
is 100 msec.
9.
Compute the data rate of the human ear from the following information. People can
hear frequencies up to 22 kHz. To capture all the information in a sound signal at 22
kHz, it is necessary to sample the sound at twice that frequency, that is, at 44 kHz. A
16-bit sample is probably enough to capture most of the auditory information (i.e., the
ear cannot distinguish more than 65,535 intensity levels).
10.
Genetic information in all living things is coded as DNA molecules. A DNA molecule
is a linear sequence of the four basic nucleotides:
A
,
C
,
G
, and
T
. The human genome
contains approximately 3
10
9
nucleotides in the form of about 30,000 genes. What
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