3. Processor And Chipset

#2: Processor

Our next item is the processor, the heart of the new Psion, which will dictate what kind of operating systems, programs, and, ultimately, what kind of functionality we can have.

The Psion 5mx has an ARM 710T running at 36.86 MHz. This is fine for the applications that came with it and others that require limited processing power. Install something more demanding like a route planner with the map of the US or Europe and you'll have to wait a considerable while before you have your driving directions. Playing an MP3 file on the Psion 5mx was an adventure only the most courageous would enter upon. You'd have to downsample the file to about 40kbps, get yourself a software player and then try to listen to it on the Psion's tiny speaker, which in itself is another problem I'll be addressing later.

Fortunately we have a reasonable array of powerful and energy efficient processors to chose from nowadays.

Let's just keep in mind the Psion 20xx will be about the same size as the old one, which means the battery compartment can't really grow that much to accommodate a bigger battery. Power consumption must therefore be a main concern.

The second main concern is the architecture we want. The original ARM is a RISC (Reduced Instruction Set computer) based architecture and is best known for its power saving features, which is why it is used for the vast majority of embedded processing tasks worldwide. You can find it in most PDAs and smartphones. Intel's Xscale processor comes from this family, as does ARM's recent Cortex-A8, with its many multimedia capabilities and impressive low power requirements in the 300-500 mW area. The ARM family of processors runs Windows Mobile, Symbian and even Linux.

Then we have the x86 architecture, which is CISC (Complex Instruction Set Computer) based and widely known to almost every PC user and even Mac users by now, as both Intel's and AMD's desktop and laptop CPUs are x86 based. Choosing this kind of architecture has the main advantage of giving the user much more freedom when choosing the operating system and applications they want to work with. However, x86 processors are not generally known for their energy efficiency and the two main manufacturers are only now beginning to show their concerns and awareness about this.

We must thus face this dilemma: more freedom and less battery time, or the opposite. Our readers clearly prefer the x86 architecture. It is understandable: you can chose to install a full operating system and the same applications you have on your desktop and take them with you, with the added simplicity of not having to learn another operating system and set of applications. This is even true for more intuitive operating systems such as Windows Mobile or Symbian. Additionally, there will be far fewer cross-computer compatibility issues to worry about with an x86 CPU in the new Psion.

Some readers like killerliz and DrRon on the forum suggested using an AMD Turion, possibly underclocked, which still would drain the batteries pretty quickly, as Wolfpack122 points out. The Turion's power range is 25w-35w. AMD however does have an x86 processor capable of much more respectable power consumption results, the Geode LX. It runs at 500 and 433 MHz and has a maximum power consumption of 3.9W and 1.8W typical. On the downside it has only 128kB of L2 cache and doesn't have support for SSE instructions. The speed could also prove insufficient.

The great majority of users however rightfully pointed out that the best processor would be Intel's Core Solo Ultra Low Voltage (ULV), which runs at more than double the speed of the Geode, yet has a maximum power of 5.5w. Some suggested the U1400 at 1.2 GHz, others the entry level U1300 at 1.06 GHz.

The U1300 just might be the best choice. It costs less. Its front side bus is 533 MHz, exactly half the speed of the CPU and a match with 533 MHz DDR2 memory. And, because its speed can be throttled back using Intel's Enhanced SpeedStep Technology (featured on both chips) it will consume even less power. Underclocking was also suggested with the option of regaining full speed when being powered by an AC power supply. This is a valid point, as every watt counts.

#2.1: Chipset

A word about the chipset: the latest Intel 945GMS Express Chipset for small form factor platforms would be ideal here, as it was specifically designed for low power Centrino processors, including the Core Solo ULV. The 945GMS Northbridge, 37.5 mm square, features a DDR2 533Mhz single channel memory interface with a maximum of 2 GB memory supported, and an integrated graphics engine (GMA 950) running at 166 MHz. The graphics engine doesn't sound like much, but for a second, more work oriented computer, it should be enough. Let's not forget the extra power a more elaborate graphics processor would require. The 945 Southbridge, 31 mm square, is the ICH7M.