Developers Say the PACE Is Fast Enough
The biggest change in Palm OS 5 is the switch from Dragonball processors to ARM-based ones. This change would have required all developers to rewrite all their applications but PalmSource knew this would be a disaster for the platform so it created the Palm Application Compatibility Environment (PACE), which interprets the instructions of existing applications designed for the Dragonball processor, and makes them run on the ARM processor. There has been some concern in the Palm community that this would make OS 5 run slower than OS 4. According to developers, this isn't the case.
PACE does not emulate the 68k Dragonball chip or other hardware, nor does it run the old operating system. Instead, it interprets the 68k instructions itself, and handles 68k trap instructions (used by applications to call OS APIs) by making calls into the native Palm OS 5 system. All the OS level calls are implemented in pure ARM code, so the OS itself is running at full ARM speed.
Palm OS 5's speed will depend greatly on what processors are being used. There are quite a few ARM-based chips available to be included in OS 5 handhelds and these range widely in speed. However, the slower processors are likely to be used only on low-end devices while the first handhelds available with OS 5 will almost certainly be high-end ones. According to rumor, Palm's first OS 5 handheld will use the 175 MHz OMAP1510 from Texas Instruments.
Still, some people are worried that OS 5 will actually be slower than OS 4. However, developers that have been able to run their applications on test boards running the new operating system aren't worried.
Unfortunately, what they can say about performance on specific hardware is constrained by non-disclosure agreements. Still, several people were able to say enough that most people's fears should be allayed.
Howard Tomlinson, the CEO of Astraware, said "From the OS 5 demos done by David Fedor at both this PalmSource Developers Conference and the one before using a demo board he had there, you can be sure that PACE will run quite adequately for all normal apps. The Zap!2000 that he showed running on it had quite a bit of custom 68k in there instead of OS calls for graphics, and that was running faster than on a normal device, so I think you can safely see that 'good' apps that call into the OS will run at least as well as on current devices, and those that are 'bad' and bypass the OS to do custom code should still be fine."
Aaron Ardiri from MobileWizardry. said, "We ran tests with Lemmings at PalmSource, and PACE was emulating faster than the API's were being implemented natively."
"PalmSource themselves showed our "pie draw function" implemented under Palm OS 4 (OS 5 compliant) running on a PACE board to illustrate the incredible speed most operations now will zip along at that were sluggish ," said Mike Compeau, VP of Business Development & Planning, Cutting Edge Software. "We are confident that those customers lucky enough to buy a copy of Quickoffice for their NEW OS 5 device will NOT have in any way a bad experience due to PACE implementation."
Despite this encouraging news, there is still room for improvement. OS 5 doesn't allow developers to write completely ARM-native applications, though they can include small bits of ARM code called ARMlets. The next version of the Palm OS, generally referred to as OS 6 though PalmSource hasn't officially given it a name, allows true ARM native apps. According to PalmSource, code that has been recompiled for ARM-based chips is 61 times faster on a 200 MHz ARM processor compared to a 33 MHz Dragonball one.
I wanted to say thanks to all the developers who helped out with this article. -Ed
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