Thin times in Soho

Thin clients are creeping back into the office, and reaching into the home, after going rapidly in and out of fashion during the network computer craze when they were vaunted as the death of all things Microsoft.

No-one would have guessed from that hype, stirred up mainly by Sun and Oracle, that thin clients are the oldest form of desktop computer; a low-power terminal acting as a front end for applications running on a server.

A Windows terminal looks to the user just like a standard PC, except that it has no local storage (although you can also get 'fat clients' with their own disks and other facilities).

The network computer differs only in that it runs applications itself, and so may need more processing power. But, like the terminal, it lacks local storage and uses code and data sitting on a server.

In both cases, hardware costs may be lower, security is tighter, and the software is easier to maintain because it sits on a single machine.

It has to be said that thin clients tend to be less popular with users in the workplace than with IT staff, who get more control over how machines are used.

Thin clients are moving into the home with the boom in wireless networking and the convergence between consumer electronics and computing.

Microsoft's Media Center Extender, which lets your TV (or some other client device) screen video or stills piped from your PC, is a thin client; so is the Smart Display, which acts as a window on a remote XP PC, although it is becoming harder to buy.

Both these products exploit a back door into Windows XP Professional called the Remote Desktop Protocol (RDP), originally designed to allow support staff to take control of a distant machine when sorting out problems.

You can use RDP software, freely downloadable from Microsoft, to turn an antique PC into a powerful thin client, allowing you, for instance, to use your XP desktop workhorse from anywhere in your home via an old Wi-Fi equipped notebook.

Organisations, particularly in the public sector, commonly defer costly hardware upgrades by doing something similar on a large scale by configuring old PCs as thin clients.

But they tend eventually to swap the PCs for 'real' thin clients to get better graphics, according to Peter Bolton, European vice president of Neoware Systems. "A resolution of 800 x 600 is no longer good enough for today's applications," he said.

Neoware, a preferred thin client supplier to IBM, has just launched a new range starting at just £129 ex VAT. You'll have to buy a monitor separately. They are targeted mainly at medium to large businesses, which can save a fortune on the cost of scores or hundreds of new PCs.

But how much sense do devices like this make on a small scale? It depends on what you want to do. And be warned that you are not necessarily going to save money, according to Paul Randle, Windows client product manager at Microsoft UK.

Thin clients can make sense for firms with several people using mobile devices on the road because both desktop and untethered machines will use the same central data store, facilitating synchronisation and maintenance.

Very small organisations might get away with a single server. Most, Randle says, would need one 'terminal server' interacting with the client machines, plus one server per department for running office applications. That means at least two server software licences, plus all the client licences.

You'd also need to be fairly skilled to set it up, and few very small business have trained, dedicated IT staff. "But we have done a lot of things with Windows Server 2003 to make it easier," explained Randle.

All this is off the scale for home users, although a modern PC is perfectly capable of running office applications for two or three thin clients at once. The family edition of Microsoft Office allows for three users but they have to use three PCs, because XP Pro's RDP currently supports only one user at a time.

The Service Pack 2 update of XP, due this summer, will allow up to five concurrent sessions of the Media Center version of XP, but only for the purposes of accessing multimedia content.

You could not, for instance, have three people writing letters using Word on the same host machine. Randle agrees that this could become an issue as home clients proliferate; even TVs are beginning to sprout keyboards.

Intriguingly, the RDP client does not need to run Windows. Some Linux-based Neoware clients, for instance, can front an XP machine. So you could have a mobile Linux device that runs organiser-style applications on the move but can act as a Windows terminal at base. It's the kind of transitional device that may be necessary if open source is ever go truly mainstream.

Linux does not need as much processing power or memory as Windows but an open source mobile is not necessarily cheaper to manufacture than a Microsoft-based notebook. "Component costs on PCs are cheaper because so many are being made," said Bolton.

One thing does seem clear: the single-user restriction on XP applications stems from a licensing rather than a technical issue. And if Microsoft does not do something about it, someone else will.