I/O Interfaces & Buses
On a link with 10 GB/s bandwidth and 1 µs latency, roughly how long does it take to send 64 bytes once (time = latency + size ÷ bandwidth)?
- AAbout 6.4 ns
- BAbout 1 µs
- CAbout 101 µs
Show answer and explanation
Answer: B. About 1 µs
64 bytes ÷ 10 GB/s = 6.4 ns, so the time is 1 µs + 0.0064 µs ≈ 1 µs, nearly all latency. Sending 1 MB instead takes 100 µs + 1 µs ≈ 101 µs, determined almost entirely by bandwidth. When sending many small pieces, more bandwidth does not help, so the remedies are batching the data or using a lower-latency link.
- A. That is the transfer time alone, without latency.
- B. Correct. It is almost entirely latency.
- C. That is close to the time for 1 MB.