PalmSource, the software subsidiary of handheld maker Palm, last week shipped the latest version of its Palm OS operating system to licensees and developers. This opens the way for handheld makers such as Palm, Handspring and Sony to release a new generation of devices based on ARM-architecture chips. But backwards compatibility may not extend as far as users and developers had hoped.

"Palm OS 5.0 is a major milestone for us, and we're happy to be delivering the final version ahead of schedule," said David Nagel, president and chief executive of PalmSource. The operating system includes an enhanced user interface, better security, new multimedia features and wireless networking, as well as compatibility with existing Palm OS software, according to PalmSource.

But the company warned last week that software written for versions of the Palm platform earlier than Palm OS 4.0 might not work with version 5.0. Palm OS 4.0 was itself only released last year, which means that many of the commercially available Palm applications could be affected.

Jamie Pyper, PalmSource's senior manager for European development services, said it had been working with developers since last autumn to make sure they updated applications to run on Palm OS 4.1. He added that PalmSource had found few problems in random testing with applications, including those written for Palm OS 3.5. "Our goal is to make sure 80 percent of popular apps are compatible," he said.

Devices running Palm OS 4.1 or below are restricted to relatively low-powered Motorola processors. Palm OS 5.0 has been written for the ARM architecture, which includes Intel's StrongArm chips as well as the newer XScale and Texas Instruments' Omap chips.

The new platform contains an emulator that runs existing Palm applications, and the firm previously made great claims for this technology. "The user won't be able to tell if they're running a new application or an old one," said David Fedor, PalmSource's architect and evangelist at the PalmSource conference last month.

Among the new features are strong data encryption and Secure Sockets Layer (SSL) services for secure email, browsing and online transactions. Palm OS 5.0 also features built-in support for the Bluetooth and 802.11b wireless standards. The user interface has been enhanced with higher-resolution icons and fonts.

"Our goal is to introduce the industry's best ARM-based handheld this autumn," said Todd Bradley, chief operating officer for Palm's Solutions Group.

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