1. Which is the very basic technique of refreshing DRAM?
A. refresh cycle
B. burst refresh
C. distributive refresh
D. software refresh
Answer: A
The DRAM needs to be periodically refreshed and the very basic technique is a special refresh cycle, during these cycles no other access is permitted. The whole chip is refreshed within a particular time period otherwise, the data will be lost.
2. How is the refresh rate calculated?
A. by refresh time
B. by the refresh cycle
C. by refresh cycle and refresh time
D. refresh frequency and refresh cycle
Answer: C
The time required for refreshing the whole chip is known as refresh time. The number of access needed to complete refresh is called the number of cycles. The number of cycles divided by the refresh time gives the refresh rate.
3. Which is the commonly used refresh rate?
A. 125 microseconds
B. 120 microseconds
C. 130 microseconds
D. 135 microseconds
Answer: A
There are two refresh rates used in common. They are a standard refresh rate of 15.6 microseconds and 125 microseconds which is the extended form.
4. How can we calculate the length of the refresh cycle?
A. twice normal access
B. thrice of normal access
C. five times normal access
D. six times of normal access
Answer: A
Each of the refresh cycles is approximately twice the length of the normal access, for example, a 70ns DRAM has a refresh cycle time of 130ns.
5. What type of error occurs in the refresh cycle of the DRAM?
A. errors in data
B. power loss
C. timing issues
D. not accessing data
Answer: C
When the refresh cycle in a DRAM is running, it will not access data, so the processor will have to wait for its data. This arises some timing issues.
6. What is the worst-case delay of the burst refresh in 4M by 1 DRAM?
A. 0.4ms
B. 0.2ms
C. 170ns
D. 180ns
Answer: B
A 4M by 1 DRAM has 1024 refresh cycles. The bursting delay will be 0.2ms that are, the worst-case delay is 1024 times larger than that of the single refresh cycle. The distributed delay is about 170ns.
7. Which refresh techniques depend on the size of time-critical code for calculating the refresh cycle?
A. burst refresh
B. distributed refresh
C. refresh cycle
D. software refresh
Answer: B
Most of the system uses the distributed method and depending on the size of the time-critical code, the number of refresh cycles can be calculated.
8. Which of the following uses a timer for the refresh technique?
A. RAS
B. CBR
C. software refresh
D. CAS
Answer: C
The software refresh acts by using a routine to periodically cycle through the memory and refresh. It uses a timer in the program to generate an interrupt. This interrupt performs the refreshing part in the DRAM.
9. What is the main disadvantage of the software refresh of the DRAM?
A. timer
B. delay
C. programming delay
D. debugging
Answer: D
Debugging in software refresh is very difficult to perform because they may stop the refreshing and if the refreshing is stopped, the contents get lost.
10. Which refresh technique is useful for low power consumption?
A. Software refresh
B. CBR
C. RAS
D. Burst refresh
Answer: B
CBR that is, CAS before RAS refresh is the one that is commonly used. It has low power consumption quality because it does not have an address bus and the buffers can be switched off. It is worked by using an internal address counter which is stored on the memory chip itself and this can be incremented periodically.
