1,000+ ASIC Interview Questions: SystemVerilog, UVM & RTL

DescriptionQ283

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Q283ArchASIC interview problem

Find the densest 4 KiB page

TechniquesAssociative arrayAddress alignmentHistogram

DifficultyEasy

TopicMemory Systems

LanguageSystemVerilog

Requirements4 checkpoints

Problem

Given an associative array keyed by written addresses, return the 4 KiB-aligned page base containing the most keys and its density.

Six addresses grouped into three aligned four-kibibyte page bins with counts — Clear the low twelve address bits to form each page base, then compare the resulting densities.

Function headerSystemVerilog

function automatic void densest_page_4kb(
  input bit [31:0] mem[longint unsigned],
  output longint unsigned densest_page,
  output int unsigned density
);

Example input and output

Use this case to check your interpretation

Input

written addresses=[0x1004,0x1010,0x1FFC,0x2000]

Output

page_base=0x1000; density=3

Explanation

The first three keys share page number 1 after shifting by 12; the fourth belongs to page 0x2000.

Requirements (4)

Count keys by shifting each address right by 12.
Return the page base, not the page number.
Return zero outputs for an empty input.
Break equal-density ties in favor of the lower page base.