Low Power – They Just Don’t get it


For a while I’ve been reading the Lenovo blog Inside The Box [1], even though I plan to keep my current laptop for a while [2] (and therefore not buy another Thinkpad for a few years) I am interested in the technology for it’s own sake and read the blog.

A recent post concerns a new desktop machine billed as “our greenest desktop ever” [3]. The post has some interesting information on recycling plastic etc, and the fact that the machine in question is physically small (a volume of 4.5L and no PCI expansion slots) means that less petro-chemicals are used in manufacture (and some of the resins used are recycled). However the electricity use is 47W when idle!!!

On my documents blog I have a post about the power use of computers I own(ed) [4] which includes my current Thinkpad (idles at 23W) and an IBM P3 desktop system which idles at 38W. Both machines in question were manufactured before Lenovo bought Thinkpad and IBM’s desktop PC business (so they technically aren’t Lenovo machines) and they weren’t manufactured with recycled resins. But the claim that the new machine is the greenest ever is at best misguided and could be regarded as deceptive.

I think that the machine is quite decent, but it’s obvious that they can do a lot better. There’s no reason that a low-power desktop machine (which uses some laptop technology) should take more than twice the power of what was a high-end laptop a few years ago. Also comparing power use with P3 machines (which are still quite useful now, my IBM P3 desktop runs 24*7 as a server) is quite relevant – and we should keep in mind that before the Pentium was released no system which an individual could afford had anything other than a simple heat-sink to cool it’s CPU.

This is largely a failing of Intel and AMD to make power efficient CPUs and chipsets. It’s also unfortunate that asymmetric multi-processing has not been implemented in recent times. A system with a 64bit CPU core of P3 performance as well as some Opteron class cores that could be suspended independently would be very good for power use with correct OS support. For example when reading documents and email my system will spend most of it’s time idling (apart from when I use Firefox which is a CPU hog) and the CPU use will be minimal for scrolling – a P3 performing core would be more than adequate for that task (which comprises a significant portion of my computer use). Then when I launch a CPU intensive task (composing a blog post in WordPress or compiling) the more powerful CPU cores could start.

It would be good if Intel would release a Pentium-M CPU (32bit) with the latest technology (smaller tracks on the silicon means less power use as well as higher clock speeds). A Pentium-M running at 2GHz produced with the latest Intel fabrication technology would probably use significantly less power than the 1.7GHz Pentium-M that is in my Thinkpad. Put that in a desktop machine and you would have all the compute power you need for most tasks other than playing games and running vista and you could get an idle power less than 23W.

The new Lenovo machine in question does sound like a nice machine, I wouldn’t mind having one for testing and running demos. But the claims made about it seem poorly justified if you know the history.

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6 thoughts on “Low Power – They Just Don’t get it”

  1. Vincent Bernat says:

    I own a Pentium-M 1.6 GHz laptop and it draws between 8 W and 12 W (from powertop, I don’t know if it is reliable). It is one of those ultra tiny laptop with 12″ screen, I855GM graphic card, etc. I don’t know if a recent laptop of the same factor with a Core 2 Duo gets the same figures. But definitely, Intel knows how to build low consumption laptops.

  2. etbe says:

    Vincent: Given that my entire system (running a 1.7GHz Pentium-M) idles at 23W (drawn from the wall – the power supply wastes some energy as heat) it seems quite reasonable that your CPU might take between 8W and 12W (while still using about the same as my 23W from the wall).

  3. alex says:

    Actually, I once read that the ecological costs of manufacturing a PC are massive compared to the power that the PC actually draws on its lifetime- so even factoring in that the new CPUs consume a lot more power, their claim of greenest PC ever might not be incorrect.

  4. Coven says:

    “before the Pentium was released no system which an individual could afford had anything other than a simple heat-sink to cool it’s CPU”

    No, that’s not really true. My 486 did have a huge heatsink AND a fan and it really needed it.

  5. etbe says:

    alex: I expect that depends on what the lifetime is. The lifetime of a PC can vary a lot, from a couple of years of a few hours a day to 6+ years of 24*7. The incidence of running PCs 24*7 is steadily increasing…

    Coven: The earlier 486 CPUs did not have fans. As far as I recall it was only the 66MHz and faster 486 class CPUs (most of which were not made by Intel who concentrated on the Pentium) that had fans. As far as I recall the Pentium-60 was the first PC CPU that had a fan, but there was only a matter of months between those CPUs, so I may be mistaken on the exact order.

  6. Vincent Bernat says:

    etbe: if I remember correctly, T40 uses ATI graphic card. Mine is using I855GM and Intel put a lot of efforts to reduce the power consumption of this chipset (with new intel driver in xorg). I think that powertop, through ACPI, reports the whole consumption, except the power supply part. Unfortunately, I don’t own a wattmeter to test the real consumption from the wall.

    Maybe you could check with powertop the difference from the reported value and the value you get with a wattmeter.

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