ITPEC FE Morning October 2018 Question 12
ITPEC FE Morning October 2018 — Question 12 of 80
Address Bus Width — determine the number of address lines for a given memory size.
1 MB = 1,024 × 1,024 = 1,048,576 bytes = 2^20 bytes.
To address each byte individually, we need 20 address lines (A0–A19).
Formula: n = log₂(memory size in bytes)
Why not others:
- (a) 18 — 2^18 = 256 KB, insufficient
- (b) 19 — 2^19 = 512 KB, insufficient
- (d) 21 — 2^21 = 2 MB, more lines than needed
Key rule: The data bus width (8 bits = D0–D7) confirms byte-level access but does not affect the address line count.
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