Sunday, January 09, 2005

For my last computer, I upgraded from a Pentium 1 MMX (200mhz) to an Athlon XP 1600 (1300mhz). It was a whole lot faster, but it was also much hotter and noisier. My old computer had one fan (in the power supply); the new one has five fans. It’s so hot I named it heater. It’s so loud that I keep it off most of the time.

Nelson recently bought a quiet PC, and that inspired me to start thinking about upgrading. For my next PC, I’d like to get something quieter, and if possible, cooler. I found a good article explaining CPU heat, comparing Pentium and Athlon systems. Summary: the Pentium wattage specs are too low and Athlon wattage specs are too high, so even though both are around 90 watts, the Athlon runs cooler.

From what I remember from electronics class, power usage is proportional to the square of voltage. But CPU speed is (I think) only proportional to voltage. So for every additional 10% in speed, you need 21% more power. Someone tries out underclocking to get the reverse effect: a small decrease in voltage (and thus speed) leads to a large decrease in power consumption. Neat!

Things that seem to matter in keeping the system quiet: how much heat is produced, how noisy the fans are, and how noisy the case is (vibrations, rattling, etc.), and how noisy the hard drive is.

Things that seem to matter in keeping the system cool: CPU wattage, GPU wattage, hard drive, and power supply efficiency. If you can get a power supply that’s 80% efficient instead of 60% efficient, that halves the heat wasted by the power supply. Have you noticed that many AC to DC adapters for consumer devices like telephones are warm to the touch? That's the wasted heat. Many cheap devices have power supplies that are only 30% efficient. Ick.

I’ll probably buy a system from instead of building one myself, as I have in the past. There are just too many things I don’t understand about air flow & turbulence, quiet hard drives, heat sinks, thermal compound, ball bearings, vibration, heat pipes, heat sinks, etc., and I’d rather pay a little more to have an expert choose parts and assemble something quiet.