Lec 4 - Memory, Stacks and Computing Architectures

Question 1

What are 3 types of ROM?

Answer 1

PROM, EPROM, EEPROM

Question 2

What does PROM stands for and why so?

Answer 2

Programmable ROM - Programmed by a once-only irreversible operation, e.g in factory

Question 3

What is EPROM?

Answer 3

Erasable Programmable ROM - Can be removed from the computer and erased and programmed (slowly) by using speical apparatus (e.g UV light)

Question 4

What are some characteristics of EPROM

Answer 4

• Sometimes called “field programmable” i.e “in the field”
• Bulk erased: every bye erased at the same time
• Byte programmable: Write bytes 1 by 1

Question 5

What is EEPROM

Answer 5

Electrically erasable ROM - Can be erased and reprogrammed byte by bye in situ, but writing slower than normal reading

Question 6

What are some variances of RAM?

Answer 6

Static RAM

Question 7

What are characteristics of static RAM?

Answer 7

Retains information until power removed. Fast, larger area of silicon per byte, modest power requirement

Question 8

What is the downside of static RAM?

Answer 8

Chunky - take up spaces and only retain when there is power. Also could be expensive

Question 9

What are characteristics of Dynamic RAM?

Answer 9

Retains information as long as the contents are refreshed frequently. Smaller area of silicon per byte, low power requirement
- Does not use flip flops
- Use tiny capacitors to store electric charge
- Because of ‘charge leak’ -> require rewrite every few miliseconds

Question 10

What are the downsides of dynamic RAM?

Answer 10

The access is slower

Question 11

What are characteristics of SDRAM?

Answer 11

• Hybrid of dynamic and static RAM
• “Clocked” by the main CPU clock

Question 12

What is DDR (double data rate) SDRAM?

Answer 12

• Chips produce data on rising and falling edges -> Register in the other state -> Double rate
• Higher data rates, e.g 64 bits/ nsec