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I've been kind of interested in the mechanics (er, electronics) of computer systems lately and after a bunch of research and looking at my computer's properties, I've come across something strange.
Most people say faster RAM means, well, faster RAM. Sounds logical right? But after looking at my computer I noticed that my installed RAM is capable of being under clocked. It usually runs at 333 Mhz (DDR2 at 667) with a 5-5-5-15 timing. However one of the programs I'm using to look into my PC says that it is capable of working at 266 Mhz with 4-4-4-12 timing and 200 Mhz with 3-3-3-9 timing.
The thing is, according to my calculations (simply the timing number divided by the clock frequency to get latency in seconds), 200 Mhz at 3-3-3-9 timing actually has better latency than 333 Mhz at 5-5-5-15 timing.
So my question is: Is this in fact true that I can actually improve the performance of my system if a program I run is accessing the memory in a truly random fashion (as opposed to sequential read/writes) by under clocking the RAM and selecting a tighter timing or have I made an error somewhere?
Edit: Just before you start arguing that I'm mistaken about RAM "speed", let me define what I mean by "faster". RAM has both latency and bandwidth. When I say "faster" I am strictly talking about latency and not bandwidth. In sequential read/writes, yes, bandwidth is much more important than latency (RAM operates in burst mode, which achieves it's maximum bandwidth by pumping sequential rows of data into CPU cache even if the CPU never asked for the extra stuff). In random access however, latency totally out rules bandwidth.
1Short answer: yes, latency has a big impact on RAM performance :) – alex – 2009-09-10T06:08:25.220
2Short answer: no. Latency is almost never as important as transfer speed. You may wait a tiny bit longer until you get the first bit of data, but you'll more than make it up by getting the last bit sooner. (You are wrong about random access. At this level, RAM cannot be accessed randomly. You can only read chunks.) – David Schwartz – 2012-11-23T23:48:33.503