The launch of Intel's low-power Atom processor earlier this year has been something of a reality check for the computer industry. For decades, most CPUs have been sold pretty much exclusively on performance. You simply bought the fastest chip your budget allowed.

Then Atom came along, said "stuff that" and unapologetically offered merely adequate performance. No nonsense about blazing multimedia performance. Just a cheap chip that gets the job done for most people, most of the time.

It's enough to make you wonder whether you've been blindly blowing way too much money on your PCs. If Atom is "good enough", who needs a pricey Core 2 processor?

Mixed messaging

In fact, Atom is such a departure from the norm even Intel's usually slick marketing operation has been struggling to keep on message. Rather bizarrely, Intel's head honcho Paul Otellini recently described the Atom as a chip that, "most of us wouldn't use."

It's into this intriguing context that plucky old VIA is launching its latest low cost CPU, the Nano. Unlike most CPUs from VIA, which typically lag behind in the performance stakes, extremely bullish noises are being made about the Nano.

Put simply, VIA reckons it's faster across the board than the Atom. Certainly, it's a more sophisticated chip than the cut-down Atom. It's a fully x86-compliant design and crucially supports out-of-order execution. The Atom is a simple in-order chip and therefore very compact but relatively inefficient in terms of work done per clock cycle.

Fine architecture

The Nano has a range of further architectural advantages such as the ability to issue three instructions per clock cycle to the Atom's two. All Nanos also support 64-bit data addressing, a feature currently only offered by a single Atom model.

In fact, the Nano's only obvious shortcoming is the lack of support for simultaneous multi-threading – Atoms, of course, support two threads courtesy of Intel's HyperThreading technology.

All in all, therefore, the Nano architecture looks like it should be capable of significantly more number crunching per clock cycle than an Atom. The Nano is also available at slightly higher frequencies. Conclusion? It jolly well ought to offer more performance.

Power consumption

The other half of the equation is power consumption. Here things look a little less auspicious for VIA's new cheapo chip. On paper, the Atom is much, much more power efficient. Intel says the maximum power consumption of any Atom is below five watts, whereas the top Nano is a 25 watt chip.

Granted, VIA and Intel measure power consumption slightly differently. But not that differently. Clearly the Nano's more complex architecture comes at a power efficiency cost. For cheap desktop systems, that probably doesn't matter. However, for low cost netbooks and notebooks, the Nano's relative gluttony could be a significant drawback, both in terms of battery life and form factors.

Anyhow, what you really want to know is how the Nano performs. Happily, that's a question we can answer. We have both the top 1.8GHz Nano L2100 and Intel's 1.6GHz Atom 230 to hand and it makes for an extremely interesting contest. Both are desktop chips aimed at so-called net-top systems.

Restrict your activities to simple web browsing or low key document editing and there's not much to choose between the two. Both are capable of running a full fat install of Microsoft's bloated Vista operating system reasonably well.

Yes, the shiny Vista interface is a little less responsive than with a Core 2 processor or one of AMD's desktop chips. But so long as you keep the open browser page count to sensible proportions, both the Nano and Atom can cope.