Monday 13 June 2022 – Afternoon

A Level Computer Science

H446/01 Computer Systems

 Time allowed: 2 hours 30 minutes

*H44601*

*8963654597*

INSTRUCTIONS

• Use black ink. You can use an HB pencil, but only for graphs and diagrams.

• Write your answer to each question in the space provided. If you need extra space use

the lined pages at the end of this booklet. The question numbers must be clearly shown.

• Answer all the questions.

INFORMATION

• The total mark for this paper is 140.

• The marks for each question are shown in brackets [ ].

• Quality of extended response will be assessed in questions marked with an asterisk (*).

• This document has 32 pages.

ADVICE

• Read each question carefully before you start your answer.

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DC (ST) 300461/3

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BLANK PAGE

PLEASE DO NOT WRITE ON THIS PAGE

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Answer all questions.

1 A charity uses a desktop computer to record financial donations that it receives. The computer

contains a single core, 2.4GHz processor with 2MB cache.

 (a) The processor uses the Von Neumann architecture.

 (i) Describe what is meant by the term ‘Von Neumann architecture’.

 ...........................................................................................................................................

 ...........................................................................................................................................

 ...........................................................................................................................................

 ...................................................................................................................................... [2]

 (ii) Give one way that the Harvard architecture differs from the Von Neumann architecture.

 ...........................................................................................................................................

 ...................................................................................................................................... [1]

 (b) The charity is concerned that the performance of the computer is not sufficient and wishes to

replace the processor.

 Give two features of a replacement processor that would increase the typical performance of

the computer.

1 ................................................................................................................................................

 ...................................................................................................................................................

2 ................................................................................................................................................

 ...................................................................................................................................................

[2]

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 (c) Fig. 1 shows assembly code written using the Little Man Computer (LMC). The program

calculates and outputs the total amount that is donated to the charity in any particular day.

Depending on the amount, an additional bonus may be added to each amount donated.

 start INP

 STA donation

 SUB hundred

 BRP bonus

 nobonus LDA total

 ADD donation

 STA total

 OUT

 BRA start

 bonus LDA total

 ADD donation

 ADD twenty

 STA total

 OUT

 BRA start

 hundred DAT 100

 twenty DAT 20

 donation DAT 0

 total DAT 0

 Fig. 1

 (i) The program shown in Fig. 1 is run once using three different inputs. Therefore, while

the program is running once, it will output the updated total three times.

 Give the total values that are output when the values 10, 50 and 120 are input into this

program.

Output for 10 .....................................................................................................................

Output for 50 .....................................................................................................................

Output for 120 ...................................................................................................................

[3]

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 (ii) Write LMC code that will reset the value of the memory location labelled total to zero

and then stop the program.

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