Tag Archives: Racetrack

At the speed of light

It is quite enlightening to look at the maximum distance that can be travelled by light (or information) within a single CPU clock tick. This has reduced from around 0.1Km in the 1970s (at 3MHz) down to 100mm now (at 3 GHz). 

In other words, for today’s CPU to request information and have it returned within a single clock tick, the information must be in the near vicinity of the CPU. Therefore, any kind of storage is going to create a storage wall no matter how fast that storage technology is (flash, racetrack, PCM etc). Even storage as fast as the CPU cache itself will still present a storage wall if it has to sit beyond the motherboard – simply because information will not be able to travel faster than the speed of light (quantum computing and entanglement aside).

Ultimately, if we do replace current hard disk and flash storage with fast non-volatile RAM we still will not have removed the access latency problems we currently see, unless all of the data can be located near the CPU itself or we abandon the von Neumann architecture that underpins the computing industry.