OCR J277 Mark Scheme - Components & Performance

OCR	GCSE (9-1) Computer Science Mark Scheme J277/01: Components, Function & Performance

Question	Answer	Marks	Guidance
1	CU: Sends signals to direct the operations... Cache: High speed memory... ALU: Performs mathematical...	3	1 mark per correct line.
2	Row 1: CU (Sends signals) Row 2: Cache (Stores frequently used) Row 3: ALU (Performs subtraction)	3	1 mark per correct tick. Note: The Control Unit coordinates components via signals.
3	Any two from: Controls/coordinates the flow of data. Sends signals to synchronize the F-E cycle. Decodes instructions. Runs the Fetch-Execute cycle.	4	Examiner's Note: "Controls the computer" is too vague. Must refer to data flow or signals.
4	Arithmetic: Addition / Subtraction / Multiplication / Division Logic: AND / OR / NOT / Comparisons (<, >, =)	4	1 mark for naming "Arithmetic" or "Logic". 1 mark for a valid example of each.
5	Cache stores frequently/recently used instructions/data. (1) ...which can be accessed faster than accessing them from RAM. (1)	2	Must link the storage (point 1) to the speed (point 2). Reject: "It makes the computer faster" without explaining how.
6a	Computer A	1
6b	It has more cache / 2MB is larger than 512KB. (1) It takes less time to fetch frequently used instructions from cache than RAM. (1)	1	Focus on the comparison of the cache sizes.
7	Cache is much faster than RAM. (1) Cache is closer to the CPU than RAM. (1) Cache stores frequently used data, whereas RAM stores currently running data. (1)	2	Award 1 mark for speed/location difference. Award 1 mark for content difference (frequently used vs currently running).