Chapter 5

Question 1

Principle of locality

Answer 1

Temporal Locality and Spatial Locality

Question 2

Temporal Locality

Answer 2

Items accessed recently are likely to be accessed again soon

• instructions in loop
• induction variable

Question 3

Spatial Locality

Answer 3

Items near those accessed recently are likely to be accessed soon

• sequential instruction access
• array data

Question 4

Taking Advantage of Locality

Answer 4

• memory hierarchy
• store on disk
• copy recently accessed(and nearby) items from disk to smaller DRAM memory
  
  • Main Memory
• copy more recently accessed(and nearby) items from the DRAM to smaller SRAM memory
  
  • Cache memory attached to the CPU

Question 5

Block(aka line)

Answer 5

unit of copying

-may be multiple words

Question 6

Memory hierarchy

Answer 6

a structure that uses multiple levels of memories; as the distance from the processor increases, the size of the memories and the access time both increase.

Question 7

hit rate

Answer 7

the fraction of memory accesses found in a level of the memory hierarchy

Question 8

miss rate

Answer 8

Th e fraction
of memory accesses not
found in a level of the
memory hierarchy

Question 9

hit time

Answer 9

Th e time
required to access a level
of the memory hierarchy,
including the time needed
to determine whether the
access is a hit or a miss

Question 10

miss penalty

Answer 10

The time
required to fetch a block
into a level of the memory
hierarchy from the lower
level, including the time
to access the block,
transmit it from one level
to the other, insert it in
the level that experienced
the miss, and then pass
the block to the requestor

Question 11

track

Answer 11

One of thousands
of concentric circles that
makes up the surface of a
magnetic disk

Question 12

sector

Answer 12

One of the
segments that make up a
track on a magnetic disk;
a sector is the smallest
amount of information
that is read or written on
a disk

Question 13

seek

Answer 13

Th e process of
positioning a read/write
head over the proper
track on a disk

Question 14

rotational latency

Answer 14

Th e time required for
the desired sector of a
disk to rotate under the
read/write head; usually
assumed to be half the
rotation time

Question 15

direct-mapped cache

Answer 15

A cache structure in
which each memory
location is mapped to
exactly one location in the
cache

Question 16

tag

Answer 16

A field in a table used
for a memory hierarchy
that contains the address
information required
to identify whether the
associated block in the
hierarchy corresponds to
a requested word

Question 17

valid bit

Answer 17

A field in
the tables of a memory
hierarchy that indicates
that the associated block
in the hierarchy contains
valid data

Question 18

cache miss

Answer 18

A request for
data from the cache that
cannot be filled because
the data is not present in
the cache

Question 19

write-through

Answer 19

A scheme in which writes
always update both the
cache and the next lower
level of the memory
hierarchy, ensuring that
data is always consistent
between the two

Question 20

write buffer

Answer 20

A queue
that holds data while
the data is waiting to be
written to memory

Question 21

write-back

Answer 21

A scheme
that handles writes by
updating values only to
the block in the cache,
then writing the modifi ed
block to the lower level
of the hierarchy when the
block is replaced

Question 22

split cache

Answer 22

A scheme
in which a level of the
memory hierarchy
is composed of two
independent caches that
operate in parallel with
each other, with one
handling instructions and
one handling data

Question 23

fully associative cache

Answer 23

A cache structure
in which a block can be
placed in any location in
the cache

Question 24

set-associative cache

Answer 24

A cache that has a fixed
number of locations (at
least two) where each
block can be placed