Test 3

Question 1

Types of Memory

Answer 1

Cache memory
RAM
ROM

Question 2

Cache Memory

Answer 2

A small high-speed (and thus high-cost) type of memory thta serves as a buffer for frequently accessed data. A very high-speed memory where data from frequently used memory locations may be temporarily stored. Connected to main memory.

Question 3

RAM (random access memory)

Answer 3

Used to store programs and data that the computer needs then executing programs. Two general types of RAM memory - Static and Dynamic.

Question 4

Dynamic RAM

Answer 4

Constructed of tiny capacitors that leak electricity. Requires a recharge every few milliseconds to maintain its data. Designers use DRAM because it is much denser (can store many bits per chip), uses less power, and generates less heat.

Question 5

Static RAM

Answer 5

Holds its contents as long as power is available. Consists of circuits similar to the D flip-flop. Is faster and more expensive than DRAM. Used more for cache memory.

Question 6

ROM (read-only memory)

Answer 6

Not volatile and always retains its data. Also used in embedded systems where the programming does not need to change. Used in many appliances, toys, and cars. Used extensively in calculators and other devices like laser printers. 5 types: ROM, PROM, EPROM, EEPROM, and flash memory.

Question 7

PROM (programmable read-only memory)

Answer 7

Can be programmed by the user with the appropriate equipment. PROMs have fuses that can be blown to program the chip. Once programmed, the data and instructions cannot be changed.

Question 8

EPROM (erasable programmable read-only memory)

Answer 8

Programmable with the added advantage of being reprogrammable (requires a special tool that emits ultraviolet light). To reprogram, the entire chip must first be erased.

Question 9

EEPROM

(electronically erasable programmable read-only memory)

Answer 9

Removes many of the disadvantages of EPROM. No special tools are required for erasure (this is performed by applying an electric field) and you can erase only portions of the chip, one byte at a time.

Question 10

Flash memory

Answer 10

Essentially EEPROM with the added benefit that data can be written or erased in blocks, removing the one-byte-at-a-time limitation. This makes flash memory faster than EEPROM. Being used in cell phones, digital cameras, and music players.

Question 11

Hierarchical Memory

Answer 11

Using a combination of memory types to provide the best performance at the best cost.

Question 12

Main Memory

Answer 12

Typically a medium-speed memory. Complemented by a very large secondary memory.

Question 13

Secondary Memory

Answer 13

Typically composed of hard disk drives containing data not directly addressable by the CPU; instead, it must have its contents transferred to main memory when the data are needed.

Question 14

Solid State

Answer 14

Flash-based hard drives that are faster and sturdier than rotating magnetic disks.

Question 15

Off-line Memory (includes tertiary memory and off-line storage)

Answer 15

Requires either human or robotic intervention before any data can be accessed; the data must be transferred from the storage media to secondary memory.

Question 16

Answer 16

The Memory Hierarchy

Question 17

Memory Hierarchy Terminology - Hit

Answer 17

The requested data residing in a given level of memory (typically, we are concerned with the hit rate only for upper levels of memory).

Question 18

Memory Hierarchy Terminology - Miss

Answer 18

The requested data is not found in the given level of memory.

Question 19

Memory Hierarchy Terminology - Hit Rate

Answer 19

The percentage of memory accesses found in a given level of memory.

Question 20

Memory Hierarchy Terminology - Miss Rate

Answer 20

The percentage of memory accesses not found in a given level of memory. Note: Miss Rate = 1 - Hit Rate.

Question 21

Memory Hierarchy Terminology - Hit Time

Answer 21

The time required to access the requested information in a given level of memory.

Question 22

Memory Hierarchy Terminology - Miss Penalty

Answer 22

The time required to process a miss, which includes replacing a block in an upper level of memory, plus the additional time to deliver the requested data to the processor. (The time to process a miss is typically significantly larger than the time to process a hit.)

Question 23

Virtual Memory

Answer 23

Non-system memory that acts as an extension to main memory. Increases the available memory your computer can use by extending the address space from RAM to the hard drive.