Q4,p3,d14. Match the following 8085 instructions with the flags :

List – I	List – II
a. XCHG	i. only carry flag is affected.
b. SUB	ii. no flags are affected.
c. STC	iii. all flags other than carry flag are affected.
d. DCR	iv. all flags are affected.

Codes :

a b c d

(A) iv i iii ii

(B) iii ii i iv

(C) ii iii i iv

(D) ii iv i iii

Answer D

Q3,p3,d14. In a dot matrix printer the time to print a character is 6 m.s ec., time to space in between characters is 2 m.sec., and the number of characters in a line are 200. The printing speed of the dot matrix printer in characters per second and the time to print a character line are given by which of the following options ?

(A) 125 chars/second and 0.8 seconds

(B) 250 chars/second and 0.6 seconds

(C) 166 chars/second and 0.8 seconds

(D) 250 chars/second and 0.4 seconds

Answer A.

It prints 200 characters in 1600x10^-3s hence  so in 1 sec it prints 200000/1600=125character/sec.

Q2,p3,d14. For switching from a CPU user mode to the supervisor mode following type of interrupt is most appropriate

(A) Internal interrupts (B) External interrupts

(C) Software interrupts (D) None of the above

Answer C.

Q1,p3,d14. A hierarchical memory system that uses cache memory has cache access time of 50 nano seconds, main memory access time of 300 nano seconds, 75% of memory requests are for read, hit ratio of 0.8 for read access and the write-through scheme is used. What will be the average access time of the system both for read and write requests ?

(A) 157.5 n.sec. (B) 110 n.sec.

(C) 75 n.sec. (D) 82.5 n.sec.

Answer B.

Let total read operations are 75.and write operations are 25.

Hit ratio of read =.8

Fitst it check cache, if fails then go for memory  access.

Total read access time 75x50x.8+75x350x.2=3000+5250=8250ns.

Total write access time=25x50x.8+25x350x.2=1000+1750ns

Average access time=(8250+2750)/100=110ns.