ITPEC FE Morning April 2020 Question 21

Erased electrically in units of blocks — flash memory is non-volatile memory that clears a whole block at a time with an electrical signal.

Flash memory grew out of EEPROM. It keeps its contents without power, so it needs no refresh. Reading is fast, but writing is slow: a cell must be erased before it is rewritten, and erasure works on a whole block rather than on single bytes. That is why it suits SSDs, USB sticks and memory cards, not caches.

Answer (c)

Why not others:

• •(a) — periodic rewriting (refresh) is how DRAM keeps the charge in its capacitors; flash is non-volatile
• •(b) — CPU cache memory is SRAM, the fastest RAM; flash writes are far too slow and wear out after a limited number of rewrites
• •(d) — erasing the whole chip with ultraviolet light through a quartz window is UV-EPROM

Key rule: Tell memory types by how data is kept and erased: DRAM refreshes, SRAM does not, EPROM erases by UV light, EEPROM electrically byte by byte, flash electrically block by block.

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