My immediate thought was are you measuring throughput or latency? The latency of reading from disk is indeed very slow compared to CPU instructions. A 3ghz cl

My immediate thought was are you measuring throughput or latency? The latency of reading from disk is indeed very slow compared to CPU instructions. A 3ghz clock speed processor is running 3 billion (3,000,000,000 cycles a second) and some instructions take 1 cycle. You get 3 cycles per nanosecond. A SSD or spinning disk access costs many multiples of cycles. Read 1 MB sequentially from SSD* 1,000,000 That's a lot of time that could be spent doing additions or looping. https://gist.github.com/jboner/2841832 https://gist.github.com/jboner/2841832