Work out the bandwidth budget for three display configurations

short · 40 min · Objective 3.2

Task

Turn resolution, refresh rate and colour depth into one number and compare it against what each of your own cables and ports can carry, so that 'it only runs at 30 Hz' becomes arithmetic rather than a mystery.

Steps

  1. Record every display output on your machine and every display you own in lab/display/ports.csv with header device,connector,version,max_resolution,max_refresh,source.
  2. Compute the approximate bandwidth for three configurations in lab/display/budget.csv with header config,pixels,refresh,bits_per_pixel,gbps -- for example 1080p at 60 Hz, 4K at 60 Hz, and 4K at 120 Hz.
  3. Compare each against your ports and record in lab/display/fits.csv with header config,port,fits,limited_by.
  4. Set one display to a lower resolution and a higher refresh rate, and then the reverse, recording what the system offered in each case in lab/display/offered.md.
  5. Write lab/display/adapter.md stating, for one conversion you could make with your own equipment, whether a passive adapter would work and why -- including the direction of the conversion.

Verify

awk -F, 'NR>1 && NF>=6 {n++} END {print n" port(s) or display(s)"}' lab/display/ports.csv
awk -F, 'NR>1 && NF>=5 {n++} END {print n" bandwidth budget(s)"}' lab/display/budget.csv
awk -F, 'NR>1 && NF>=4 {n++} END {print n" fit assessment(s)"}' lab/display/fits.csv
awk -F, 'NR>1 && tolower($3)=="no" {n++} END {print n+0" configuration(s) that do not fit"}' lab/display/fits.csv
grep -c . lab/display/offered.md
grep -Eic 'passive|active' lab/display/adapter.md

Two or more ports recorded, three budgets computed, three fit assessments with at least one failing, and both notes present. If every configuration fits, compute one that does not -- 4K at 144 Hz will do it on most equipment.

Notes

The arithmetic does not need to be exact. Getting within a factor that distinguishes 'comfortably fits' from 'exceeds the link' is the whole skill, and it is what answers the exam's questions about refresh rate ceilings.

This is an independent study companion for CompTIA A+ Core 1 220-1201 and is not produced by or endorsed by CompTIA.