The Computer’s Rate Limiting Step

Back when I was still working in the pharmacology lab doing chem work, there was a term used when researching biological pathways, Rate Limiting Step. In a complex biological system with multiple steps and feedback loops you would need to determine how fast the reaction could occur. Often times you would find pathways that were essentially one way because the forward path would be so much faster than the reverse. In these systems you measure the rate of the overall system by the speed of the slowest part, ie. the rate limiting step.

The key piece of this idea is that it doesn’t matter how much faster you make steps 1,2,3, or 4 if step 5 is the rate limiting step. The overall system will get no faster. Unless you increase the rate of step 5 the system just can’t move any quicker as intermediates pool at step 4 and have to wait to be processed by step 5.

Now that I’m working with computers I’ve found that a user’s experience with a computer works the same way. CPUs and memory have been getting faster and faster every year so that people can do increasingly more complex things with their computers. Other parts of the PC have not faired as well though. Hard Disks have not been able to increase their speeds at the same rate as other parts of the system even while their capacities have skyrocketed.

However, the area of the PC that has become the rate limiting step in the average person’s computer is now the internet network bandwidth. The Internet has become such a core part of the computer and while the computer itself has become enormously faster, the internet connection just hasn’t increased at the same rate. When you’re uploading photos or downloading music and videos, it just doesn’t matter how fast your computer is anymore. Any computer produced in the last 2 years will do just fine. What will make the bigger difference has more to do with the whether your on T1 or dsl or dialup.

This has some interesting implications when it comes to computer sales. I believe that we’ve hit a plateau with CPUs for now. Intel and AMD are trying to hold onto something new with all of the multi-core marketing, but for the vast majority of people, it’s just not going to make a difference. Computers have become a commodity, the models that are still taking a premium involve higher quality and not necessarily higher performance.

The next leap in computing performance is going to involve companies building infrastructure and providing content and applications. Not sure if the Telcos are going to be able to lead the way here, they’re so much better at slowing or stopping innovation rather than driving it. It will be exciting to see who can lead the charge here.