Posts Tagged “power”

After discovering that Hauppauge WinTV NOVA-T PCI cards seem to draw anything up to 9 watts each when in operation, I’ve been theorising about ways and means to reduce the overall power consumption of a MythTV ‘backend’ server.

One option I considered was replacing two NOVA-T cards with a single NOVA-T 500 which has two tuners. The glaring problem with that approach is that I have no means of knowing before-hand whether the NOVA-T 500 doesn’t just draw twice as much power as a normal NOVA-T.

The other alternative I’ve considered is a NOVA-T USB Stick. It’s a really simple device involving a USB connector at one end and an aerial connector at the other. In theory, the limitations of the USB system should dictate that one of these sticks will not require more than 2.5 watts (more likely no more than 2 watts).

Hauppage NOVA-T USB stick

If so, I would be limited to one stick per USB slot but that’s no great hardship as I have at least four USB slots to play with.

There is a catch though, having done some reading out on the intertubes, it appears there is a problem with tuning on the NOVA-T sticks and the current version of Mythbuntu (which I have used to configure MythTV systems up until now)

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According to an article at geek.com, Fujitsu reckon they are going to demo a PC at CeBIT 2009 which will idle/sleep at zero watts ie: no current draw whatsoever.

The article speculates that this system will still be able to interact with LAN/PAN devices while ‘asleep’. This definitely runs into ‘believe it when I see it’ territory for me. It’s not that I don’t want Fujitsu to have accomplished this; computers definitely need to draw much less power when idle, but it’s a hell of a technical mountain to climb.

The whole notion of a NIC being able to respond without power only when polled intentionally just seems ever so slightly far fetched.

If you’re going to CeBIT on 3-8 March 2009, you’ll probably be treated to a demo of just how this works. Still I hope they demonstrate the device as coupled up to a proper metering device. I wouldn’t want to think that this is all just marketing and spin ;)

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The other day, I took a walk into town and purchased one of these plug-in power meters. A relatively simple affair which you plug into the socket and then plug your device into. It has a digital display which, amongst other things, can display the instant Watts drawn by the connected device. This is exactly what I needed as I’ve been eager to find out how much power various devices around the home and office draw (and hence how much they cost to run ;) )

The meter seems fairly accurate on the Watts front. I tested it with some normal filament bulbs and the reading was just a few Watts higher than their ratings as is to be expected.

I then went on to test a NAS (Network Attached Storage) device which I had recently thrown together using an old Via Epia 800 Mini-ITX motherboard, a 80GB Maxtor* hard drive, a CD-ROM drive, a USB key and a Mini-ITX specific case with a 90W ATX PSU.

The software I used was FreeNAS 0.686.4. I used this version rather than the ‘bleeding-edge’ beta as I wanted to have the Wake-on-LAN functionality which now apparently missing on the latest version. FreeNAS boots from the CDROM and stores it’s configuration settings on the USB key. The whole lot runs headless and is configured by a lovely web interface.

FreeNAS

Now; back to the power meter :)

I plugged the NAS into the meter and started it up. During boot, the system was drawing 50-55Watts and settled back to about 39 Watts on completion of the boot. This would tally with a reduced load on the CPU and the CDROM having spun down. When copying files at full-speed – the network interface is 100Base-T, the power consumption reaches the high 40s.

When idling, FreeNAS tries to conserve power. Unfortunately, the Epia 800 doesn’t seem to have any frequency stepping features and presumably maintains it’s normal 800Mhz clock speed. The hard drive does spin down and this brings current draw down to about 28 Watts – not too bad considering this is one of the older Mini-ITX boards.

Power meter - Sorry for the manky looking plug!

Power meter - Sorry for the manky looking plug!

Shockingly, however, when switched off the system is still drawing between 3 and 5 Watts. I haven’t been able to ascertain what causes the fluctation (signalling on the NIC perhaps or a dodgey PSU?) but it’s less than ideal to have it draw so much power when it is not in use.

I think I’ll spend some time looking at other hardware options for FreeNAS, possibly booting entirely from the USB key and eliminating the 5.25in CDROM would help. Other than that, I’d probably be looking at newer Epia boards to increase the energy saving.

*Yeah, I know, I wouldn’t normally use a Maxtor either but this one was donated. :P

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