Energy efficient microprocessors for PCs?

April 12, 2007 11:00 AM

What are the most energy-efficient microprocessors currently available in mass-market PCs/laptops?

I would like to know the names of the most energy-efficient microprocessors currently available (either as a standard feature or as an optional upgrade). For the time being, I'm only interested in processors available to consumers through the mass market, and not in processors that could theoretically be used in custom boxes.

posted by nyterrant to computers & internet (5 comments total)

What is your definition of "energy efficient"? If your goal is to consume as little possible, then buy a laptop with the slowest processor you can find. (But you won't like it.)

If your definition is MIPS/Watt, then it's a lot more complicated to calculate.
posted by Steven C. Den Beste at 11:55 AM on April 12, 2007

I couldn't find any TDP (thermal design power) charts, but that would be the spec to look for.

I'm probably not current but I think the VIA Eden-N has the lowest TDP of x86 processors, which is 2.5W-7W depending on clock speed.

Heres a wikipedia article that lists the TDP of the Intel Core2 line. Looks like the Merom Core 2 LV L7200 has the lowest TDP of 17W.

Similar chart for the AMD 64X2 line
posted by mphuie at 12:06 PM on April 12, 2007

The buzzword du jour you are looking for is performance per watt. This metric relates processing power to power consumption, and is one of the ways energy efficiency in microprocessors is measured.

As you probably know, a 1 Ghz Pentium is not necessarily as "powerful" as a 1 Ghz Athlon or a 1 Ghz Power5 chip, or a 1 Ghz PowerPC. (see this Wikipedia article on the Megahertz myth, and how it's come to bite Intel now that they are lowering clock speeds in their multi-core designs.)

It's also hard to compare a dual core Xeon at 2 Ghz with a Core 2 Duo which goes in laptops, also running at 2 Ghz.

What are you looking for exactly? Low power consumption? Put a 8086 cpu in a laptop. Processing power, with low power consumption? Use a low power Woodcrest.

Performance/power in a reasonable balance? The Core 2 Duo is a likely candidate. There are of course "specialty" cpus like the Crusoe and its successors, but you'll see they don't give you a huge benefit, as GPUs, displays and drives also need to be powered.
posted by lodev at 12:29 PM on April 12, 2007

I'd say the Core Duo/Core 2 Duo is a likely candidate as well.

You might find this article interesting: iMac 17" review, by Silent PC Review.

Specifically they note: With a maximum power draw of 63W, the iMac certainly qualifies as a low power system. At idle, the system drew 46W, which will qualify for approval from EnergyStar if their current draft computer spec makes it to the planned 2007 release. Even better, the system falls back into a low power mode after being left alone for a few minutes, dropping the power even more to just 33W. By way of comparison, the lowest idle power consumption we've ever seen from a custom built system is 36W — and that doesn't include an LCD monitor.

SPCR is an interesting site. Their main aim is very quiet machines, ie without loud fans and such, but energy efficient processors are very much in line with that. More efficient processors take less power which produces less heat which, for the SPCR guys, means less need for very loud CPU fans.

If I were to buy a system today with energy efficiency in mind I'd seriously consider the 17" iMac. If I were building a system myself I'd use the Intel Core 2 Duo processor, but based on that review it's going to be hard for any DIY system to meet the efficiency Apple achieved with that model. There are tradeoffs with the iMac, however, and rumors are hinting that the line may be updated soon, possibly dropping the 17" model.
posted by 6550 at 2:00 PM on April 12, 2007

It depends what you want to do. If you have floating point work, the GPUs are going to be hands down winners despite their thirst for power since they crank out such scary floating point performance.
posted by chairface at 2:07 PM on April 12, 2007