ITPEC FE Morning April 2019 Question 10

Topic: Computer Component

Which of the following is an appropriate characteristic of SRAM compared to DRAM? Here, SRAM and DRAM are compared in products manufactured in the same or similar semiconductor geometric process.

a)SRAM consumes more power, particularly when idle, compared to DRAM.b)SRAM is non-volatile, whereas DRAM is volatile.c)SRAM needs to be refreshed, whereas DRAM does not.d)SRAM uses more transistors in a memory cell compared to DRAM.

Explanation

SRAM uses more transistors per cell — an SRAM cell is a flip-flop of about six transistors, while a DRAM cell is one transistor and one capacitor.

•SRAM keeps each bit in a flip-flop, so it holds data without refresh as long as power is on. It is fast but takes more area per bit, so it is used for cache memory.
•DRAM keeps each bit as charge in a capacitor, which leaks, so it must be refreshed periodically. Its small cell gives high density and low cost per bit, so it is used for main memory.

Answer (d)

Why not others:

•(a) — SRAM draws little power when idle, since it needs no refresh; DRAM keeps spending power on refresh even when not accessed
•(b) — both are volatile: they lose their data when power is removed
•(c) — reversed: DRAM needs refresh because its capacitors leak; SRAM does not

Key rule: SRAM: flip-flop, more transistors, no refresh, fast, cache. DRAM: capacitor, one transistor, refresh, dense, main memory. Both are volatile.

Computer Component · AI-written, may contain errors

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