Hardware Reference
In-Depth Information
42.
A PCI Express system has 10 Mbps links (gross capacity). How many signal wires are
needed in each direction for 16x operation? What is the gross capacity each way?
What is the net capacity each way?
43.
A computer has instructions that each require two bus cycles, one to fetch the instruc-
tion and one to fetch the data. Each bus cycle takes 10 nsec and each instruction takes
20 nsec (i.e., the internal processing time is negligible). The computer also has a disk
with 2048 512-byte sectors per track. Disk rotation time is 5 msec. To what percent of
its normal speed is the computer reduced during a DMA transfer if each 32-bit DMA
transfer takes one bus cycle?
44.
The maximum payload of an isochronous data packet on the USB bus is 1023 bytes.
Assuming that a device may send only one data packet per frame, what is the maxi-
mum bandwidth for a single isochronous device?
45.
What would the effect be of adding a third input line to the
NAND
gate selecting the
PIO of Fig. 3-61(b) if this new line were connected to
A13
?
46.
Write a program to simulate the behavior of an
m
n
array of two-input
NAND
gates.
This circuit, contained on a chip, has
j
input pins and
k
output pins. The values of
j
,
k
,
m
, and
n
are compile-time parameters of the simulation. The program should start off
by reading in a ''wiring list,'' each wire of which specifies an input and an output. An
input is either one of the
j
input pins or the output of some
NAND
gate. An output is ei-
ther one of the
k
output pins or an input to some
NAND
gate. Unused inputs are logical
1. After reading in the wiring list, the program should print the output for each of the
2
j
possible inputs. Gate array chips like this one are widely used for putting custom
circuits on a chip because most of the work (depositing the gate array on the chip) is
independent of the circuit to be implemented. Only the wiring is specific to each de-
sign.
47.
Write a program in your favorite programming language to read in two arbitrary
Boolean expressions and see if they represent the same function. The input language
should include single letters, as Boolean variables, the operands
AND
,
OR
, and
NOT
, and
parentheses. Each expression should fit on one input line. The program should com-
pute the truth tables for both functions and compare them.
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