Numbers To Know hard
Modern DDR4/DDR5 RAM channels typical deliver bandwidth in what range?
- A 1 to 5 GB/s
- B 20 to 50 GB/s per channel
- C approximately 1 TB/s
- D approximately 100 MB/s
Answer: B. 20 to 50 GB/s per channel
Memory bandwidth is the speed at which data can be read from or written to RAM by the processor. A single channel of modern DDR4-3200 memory provides a maximum theoretical bandwidth of about 25.6 GB/s. High-end servers use 'multi-channel' configurations (often 8 channels), which can push the total system bandwidth to over 200 GB/s. However, as CPU core counts continue to rise, the 'Memory Wall' becomes a real problem—where the CPU cores are so fast that they spend most of their time waiting for the relatively 'slow' RAM to deliver the data they need to process.
One system design question a day, with spaced repetition so the ones you miss come back.
Get the appRelated questions
- What is the maximum allowed downtime per year for a system targeting '99.9%' (Three Nines) availability?
- What is the typical size of a standard ASCII character (e.g., 'A')?
- What is the typical Round Trip Time (RTT) for a single network packet traveling between New York and London (Transatlantic)?
- Network bandwidth is usually denoted in **bits** per second (Gbps), while storage is in **Bytes** (GB). What is the conversion ratio?
- Storing a password using a secure algorithm like bcrypt (cost 10) or Argon2 typically consumes how much storage per user?
- How much power does a typical fully-loaded rack-mount server consume?