A technology blog for The Economist Group IT team

Thursday, July 24, 2003

XP can damage your CPU

Really! Take a look at this item form the latest edition of Fred Langa's LangaList newsletter. Some other interesting stuff in there including a link to updated Power Toys for XP (inlcudes TweakUI). The article in Information Week referred to reminded me of the first 1GHz chip. It was a DEC Alpha and it was "clocked" by a company (whose name eludes me at the moment) that sold refrigerated units with all the processor components included. The Alpha chip was ahead of its time speed wise anyway (with clock speeds of around double the fastest AMD/Intel offerings) and still lives on with the upcoming Itanium from Intel.

This article from Hardware Central outlines how you can have a go at supercooling today (not using your office PC, please).


In the item on 802.3af I said that the maximum allowed voltage was 5V; in fact it's 48V (which makes sense as that's what digital 'phones use). The Guardian has a very positive piece on the standard and a link to PocketWatch, whose software is a kind of PCAnywhere client for your mobile 'phone.

For those that didn't read the original post fully, this is power over ethernet, not ethernet over power lines.
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Tuesday, July 15, 2003

Underground technology - part 1

London Underground (LUL) are piloting a system that will allow staff to be alerted to odd behaviour on stations, reports the Times. It works by comparing images as time passes, so that, for example, it can identify someone who is loitering by recognising that they have remained in the same position without getting on a train. Less advanced technology has been in use for some time now to save on video tapes connected to CCTV systems, so that only images that change are recorded. Still a bit big brother, though. It's being trialled at Liverpool Street and Mile End, so watch out you central Line commuters!

Underground technology - part 2

Well, not really underground specific, but even though we all know that most ATMs run Windows, it's still funny to see a Windows DHCP error dialogue box "Could not obtain IP address" on one. Spotted on the Nationwide ATM in the booking hall at Green Park station this morning.
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Thursday, July 10, 2003

Wireless power

Well not quite, but this BBC article has a good overview of the 802.3af standard for carrying power over twisted pair Ethernet cable, known as power over LAN (PoL). This standard has virtually been ratified by the IEEE and lots of manufacturers have products that support power over ethernet, such as Cisco, 3COM and PowerDsine.

It works by using the spare pairs of wires in Ethernet 10baseT cabling. For those that don't know, the generic term for the cabling that is widely used for Ethernet these days is unshielded twisted pair (UTP). A UTP cable consists of eight wires which are twisted together in pairs at different twist densities so that interference between pairs is reduced. The greater the number of twists per inch for the whole cable the more data it can carry. So, for example category 5 cable (CAT5) is suitable for for 100Mbps Ethernet, whereas CAT4, with a lower twist density (and therefore cheaper) is only suitable for 10Mbps Ethernet. The IEEE specification for Ethernet over UTP specifies that two pairs of the four are needed, leaving two spare. If you look at an RJ45 jack on the end of some CAT5 cable you'll see that it has eight pins. Pins 1 & 2 (striped orange & orange) and pins 3 & 6 (striped green and green) are used for 10baseT. The other pins are connected to the spare pairs which the 802.3af standard uses.

So what's the catch? Well, as you may have guessed you can't push 240V down a 10baseT cable (well you may be able to but it's not advisable). 802.3af specifies up to 5V DC and 12W - not enough to power your PC and monitor, but enough to power an IP 'phone, for example or a wireless access point. In other words, PoL is useful for when you need to install something where you wouldn't already have power (i.e. a security camera) or where you wouldn't want the expense of running additional power. An important point to remember with digital and IP 'phones, too is that they don't work when there's no power. Typically if you have an installed base of digital 'phones (which are powered from the switch at around 50V) you need to have 10% in number of normal analogue direct exchange lines for use in an emergency in case of a power failure (your normal home 'phone line carries around 12V). PoL can help with this if you have your core network protected by UPS and generators.

If you're interested in reading more, Slashdot has had dicsusssions on the technology in the past. I'm looking forward to power over WLAN.
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