Home Syncing your handheld: USB vs. serial

Syncing your handheld: USB vs. serial

Scott Wasson Former Editor-in-Chief Author expertise
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Of course, handhelds are much more than just personal organizers. With additional software, you can use a handheld computer to read web pages, play games, or edit documents and spreadsheets, and that’s just the tip of the iceberg. A PC connection is necessary to install the software, and the Internet-ready software typically uses the PC as a conduit to the ‘net. Clearly, increasing the functionality of your handheld relies on a PC connection, as well. So what options are there for connecting to a PC?

Connection choices
There are several ways to connect a handheld with a computer for syncing purposes. Among these technologies, serial and USB interfaces are the most prevalent with modem and IR syncing being used much less frequently. Some handhelds support only USB connectivity, some only serial connections; the Handspring series supports both. Not only does this make the Handspring series versatile, it also makes it a perfect platform on which to test USB vs. serial connectivity.

The first and only Palm-based handhelds to offer true USB support, the Handspring line comes with a USB syncing cradle; an optional serial cradle is available for those without USB support. Palm actually offers an optional USB syncing solution, but it doesn’t offer ‘true’ USB functionality and is instead a USB adapter for its serial synccing interface. Despite using a USB port on the PC to connect, Palm’s USB cradle still only syncs at serial speeds. Handspring, on the other hand, takes advantage of USB’s higher bandwidth, claiming speeds of up to 4 times that of a serial interface.

Is Handspring’s USB cradle really four times faster than their serial offering? Do applications see better results from a fatter syncing pipe? If USB really is faster than serial, are the gains really big enough to make much of a difference in real world use? Let’s find out.

Test machines

The PC:

  • AMD Athlon (T-bird) at 800MHz
  • Abit KT7-RAID motherboard
  • 256MB PC133 SDRAM
    2 x Maxtor 20GB hard drives (RAID 1)
    Windows 2000 SP1

The handheld:

  • Handspring Visor Deluxe
  • PalmOS 3.1H
  • Handspring serial and USB cradles

The tests
So how do you test the sync speed of a handheld’s cradle? Well, there aren’t any benchmarking programs out there, so I had to go old school on this one. Testing was as simple as using a stopwatch to time the syncing process from the moment a sync connection was established to the moment the syncing process ended. Trials were run several times to ensure that results were consistent and that there was no interference from other processes. Tests were also designed to isolate specific types of sync loads.

We used the latest version of the Palm Desktop syncing software available from Handspring’s web site. To sync with Outlook 2000, we used Intellisync version 3.7. Intellisync offers more options than the standard Palm Desktop Outlook conduit, making it more useful in the real world. Additionally, InstallBuddy and BackupBuddy software were used for both standard syncing and for all installation benchmarks. InstallBuddy’s impact on the tests is minimal, but BackupBuddy’s presence is definitely felt.

BackupBuddy is a software package that gives you an extra layer of backup protection for your handheld by backing up settings and programs that aren’t normally backed up with standard synchronization software. Unlike a standard sync, BackupBuddy gives you a backup which can completely restore the Visor’s configuration and software, even after a hard reset. Because BackupBuddy adds an additional layer of data transfer, any speed increases seen by a USB cradle should be more apparent.

People use their handhelds for a wide range of tasks, and the amount of data synchronized differs from user to user. It would be impossible to come up with a series of tests to satisfy everyone’s curiosity on every front, but I’ve tried to design tests that reflect the different types of syncing loads in the most commonly used areas.


Hard-reset restore
The hard-reset restore benchmark involves completely wiping the memory on the handheld and then syncing it with the PC using BackupBuddy. As I’ve mentioned, BackupBuddy allows for all settings, software, and files to be restored after a hard-reset. For the sake of testing the full capacity of the handheld, I filled the memory to 99% capacity (8120 of a possible 8192 kilobytes).

The results are striking. While the USB doesn’t manage to reach its claimed 4X speed advantage, it does slog through the test 3.2 times faster than the serial connection. One thing to notice with this test is the incredible length of time it takes to do a complete hard-reset restore on an 8MB handheld. This isn’t the kind of thing you’re going to want to be doing very often, not only because it takes so much time, but also because you’ll lose everything since your last hotsync.

The serial cradle really hurts here, taking 2421 seconds—or over forty minutes—to complete the synchronization. The USB cradle’s twelve minute sync time isn’t anything to write home about, either. It’s clear that a hard-reset restore is an exercise in patience whichever cradle you use. That said, finding and reinstalling all the hacks and software not normally backed up could easily take forty minutes, so the convenience outweighs the large sync time.

Twelve minutes is obviously preferable to forty, regardless. In the unlikely event you have to do a hard-reset restore, the USB cradle is obviously what you want to be using.

Full AvantGo refresh
AvantGo is one of the most useful and popular applications for the PalmOS (PocketPC versions are also available). AvantGo allows you to download web content onto your handheld, and is a must for anyone who wants to catch up on his web reading when not at the computer. The problem with benchmarking AvantGo is that its default is to only refresh web content which has changed since the last synchronization. Because AvantGo depends heavily on the speed of the net connection used, tests were done on a cable modem connection in the early morning hours when download speeds would be the most consistent. Additionally, AvantGo was set to refresh all of its content rather than just updated pages. While this resulted in the entire cache being refreshed, it ensured that the same data would be synced each time. The test was conducted with a more typical handheld configuration with 41.1% free memory.

USB obviously wins this race, but the margin is much smaller than what we saw with the hard-reset restore. Coming in at only 2.33 times faster than a serial connection, the USB cradle doesn’t get close to the theoretical 4X speed gain. Of course, the nature of AvantGo makes the Internet connection an essential part of the speed equation. The benchmark syncs a full complement of AvantGo pages—470 individual pages in total. While the USB cradle does halve the speed of a hotsync, we’re dealing with a more common syncing process that only takes 1:41 with the USB and 3:55 with the serial cradle. An extra 2:10 might not be that big of a deal for a full AvantGo refresh, considering a full refresh is rare to begin with.


Email sync
I use my handheld for email all the time. Without a wireless connection, it’s impossible to send and receive email on the fly, but you can download email from your inbox or other folders, reply to it, compose new messages, and upload them to your outbox with every hotsync. For the email sync benchmark, I tagged 20 messages as unread in five different folders, giving me a total of 100 unread messages. Using the Intellisync 3.6 conduit with Outlook 2000 set to download all unread messages, I timed hotsync operations for the same 100 unread email messages for both USB and serial. For this and all subsequent tests, the AvantGo sync was disabled to completely remove the PC’s internet connection as a variable.

The USB interface performs admirably here, besting the serial connection by almost five minutes. The USB cradle ends up being 4.3 times faster than its serial counterpart, and finally reaches Handspring’s advertised 4X speed advantage. While 100 emails is more than I’d usually sync—a lot more—the emails only added 475K to the Visor’s memory, dropping the free space from 41.1% to 35.3%. Now USB has a much fatter pipe, but there’s something else going on here, because 475k isn’t a hell of a lot to be passing down that pipe.

The hotsync process doesn’t just dump files onto the Visor; it synchronizes them with the Visor’s mail database and converts them into a format that the mail software can understand. The email sync represents 100 files that not only must be converted, but also must be integrated with a Palm database. Since any conversion processing should be independent of the syncing interface used, the slowdown shown by the serial cradle probably has a lot to do with how the files are transferred. I can only conclude that each email is being processed and sent individually. Instead of having one transfer of 100 emails, there are 100 separate transfers. USB has an obvious edge here, as it’s able to quickly start and get through small transfers while the serial connection takes significantly longer to get wound up and through the numerous, small transfers.

Etext installation
One of the best things about the Visor (and handhelds in general) is the ability to store etexts for your reading pleasure. Etexts are not only great to read, they also make a good benchmarking tool, since they’re generally a single, large file. For this benchmark, I installed a 1,924k etext on to the Visor. Since the original format for etexts is plain text, there was some conversion that needed to be done to turn the file into a Palm document that the Visor can read. That conversion is done on the PC before any syncing takes place, though, and therefore doesn’t have any impact on the results.

Wow, USB really ripped through the etext, beating the serial interface by a whopping eighteen minutes. It took a while with both interfaces, but the USB cradle was able to complete the task 5.15 times faster than the serial connection. While we saw USB take a big lead with the email sync, this win for USB comes under totally different conditions. Since all the processing to get the etext into the Palm document format is done on the PC, this test is all about how fat the pipe is.

So why does USB do so well in comparison to other tests we’ve run thus far? This is about the simplest benchmark testing the raw speed of the syncing interface. Because we’re just dumping a document file on to the Visor, there’s really no synchronization; it’s just a straight file copy. Also, unlike AvantGo and email syncs which deal with multiple pages or emails, this is a single file big enough to let both interfaces wind up to their top speeds. As you can see, USB is faster than the advertised 4X serial speed for large single file transfers.


Dreadling installation
PDAs aren’t all about work; you can also have a lot of fun with them. With such a wealth of software out there for the PalmOS, I’m constantly installing new programs on my Visor. Since this is something I do on such a regular basis, it’s something worthy of a test. Like the etext installation, installation of a program on the Visor requires not much more than a single file copy. In the case of programs. however, actual file sizes tend to be much smaller. The program I used for this benchmark, Dreadling (the best fps for the PalmOS, probably the only one actually), weighs in at only 78k. We saw how USB trounced the serial connection for large single file transfers, this test will give us a good idea of how the cradles handle single file transfers that are a little more reasonable in size.

Not much of an advantage for USB when it comes to small files. While USB is 1.49 times as fast as serial in this test, that works out to only a 28 second advantage. USB has a fat pipe, but for small files like the 78k Dreadling install, the benefits of USB’s speed aren’t fully realized. Unfortunately, for all its claimed 4X speeds, there are some instances where USB will only be marginally faster than a serial interface.

QuickWord installation and sync
My Visor’s not all for the fun and games of Dreadling; I also use it to do real work. The QuickWord benchmarks are twofold. The first will test how long it takes to install a QuickWord document file on to the Visor; this test is pretty much identical to the etext installation, except the file size is a much more realistic 682K originating from a 1,245,273 character Word document.

USB doesn’t manage to hit its 4X serial advertised speed, but it does get close being 3.41 times faster than the serial cradle. We see USB with a clear speed advantage here for the same reasons it performed so well with the etext installation. It was still a single file dump for the most part with some additional synchronizing needing to be done to add it to QuickWord’s category filing system. The more the file size increases for such a transfer, the more the USB interface gets to flaunt its peak transfer rate.

The second test is where things get interesting, as QuickWord is able to synchronize changes made to documents. I decided to replace all the instances of the letter ‘e’ in the document with the letter ‘b’ and then do a hotsync to update the document on the Visor. The letter ‘e’ ended up replacing ‘b’ 139,142 times—enough to give the synchronization capabilities of QuickWord a good workout. Both the installation and syncing take place through the QuickOffice conduit for Word 2000.

USB has the advantage here, but its advantage shrinks as it’s synchronizing only the changes to the document and not the entire thing. Only able to perform the hotsync 2.74 times faster than the serial interface, the USB cradle does well, but its strengths clearly lie with file transfers rather than synchronization.

One interesting result to note is that the USB cradle takes longer to sync the QuickWord document than it does to copy it to the Visor in the first place. Conversely, the serial cradle syncs the document faster than it can copy it. What does all that actually mean? Because syncing a document involves more making changes than actual wholesale copying, a lot of processing goes into the syncing process. In this case, it could be faster to simply delete the file off the Visor and copy it over again with USB than to actually sync it over USB. Then again, the convenience of syncing is somewhat lost that way.


QuickSheet installation and sync
Like its word processing counterpart, QuickSheet is a conduit for Office 2000, but deals with spreadsheets from Excel rather than document files from Word. The tests here will mirror what was done with QuickWord, first the installation of a QuickSheet spreadsheet, then a synchronization of changes made to the sheet. The file used for these tests was a 2,600 cell spreadsheet. Weighing in at 96K, the spreadsheet isn’t nearly as big as our doc file, but spreadsheets are more complex than document files and should take longer to convert and sync with the Visor. Just to make things interesting, I based all the values of the spreadsheet off the value of a single cell. Doing this made it incredibly easy to change the values in the spreadsheet for the second hotsync, since all I had to do was change a single number. Effectively, the second hotsync is a wholly different spreadsheet; the formulas are the same, but every single value is different.

We’re dealing with a physically small file here, but it still takes quite a while to do the sync for both the USB and serial cradles. USB manages only 1.45 times the speed of USB, but both interfaces come in at over four minutes for a tiny, 96K file. What’s the moral of this story? QuickSheet spends far more time processing spreadsheet files rather than actually copying them. The USB and serial cradles are equally hampered by this processing time.

USB squeaks out a victory here at only 1.23 times faster than its serial counterpart. Again we see processing playing a major role keeping both sync times high. As with QuickWord, USB synchronization is actually slower than copying the file. You’re better off deleting a spreadsheet off the handheld and copying the new version over rather than trying to reconcile changes made with a hotsync—that is, if speed is your only concern.


As expected, USB is faster than serial in all of the tests. However, what I didn’t expect was to see USB reach its advertised 4X advantage over the serial interface so rarely. In only two of nine tests did we see USB reach speeds in excess of four times the speed of the serial cradle. That said, 2X or 3X speed advantages are quite respectable. If you sync as often as I do (and tend to run as late as I do), even seconds can count with a hotsync, let alone minutes.

If you use your handheld a lot for email, etexts, or large files, you’re likely to get the most out of a USB interface. With Handspring making the USB cradle standard on all of its handhelds (with the exception of the Visor Solo, which doesn’t have a cradle at all) you’re pretty much good to go. For those relegated to the serial cradle, at least you have the option. The cradle gives you full NT 4 support, and provides compatibility with older computers. Serial doesn’t do that badly either—at least, not as badly as Handspring’s literature would have you think. That said, I wouldn’t want to do any 40 minute hard-reset restores on a serial cradle if USB were an option.

USB is a pretty good feature for handhelds. Unfortunately, Palm has yet to release a true USB syncing option (though it has announced USB support for future products). How much of a difference USB will make for you will depend on what you use your handheld for and how important a couple of minutes are for a hotsync. If USB were really four times faster than serial for hotsyncing, I’d chose a product supporting USB over one that didn’t without question. However, seeing as the average speed advantage in our tests was only 2.81X, USB isn’t as clear cut a winner as it’s presented to be. Personally, I’d still go for a USB product, all things being equal, but of course that’s rarely the case.

So you’ve got some USB vs serial data; now, the choice is up to you. 

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Scott Wasson Former Editor-in-Chief

Scott Wasson Former Editor-in-Chief

Scott Wasson is a veteran in the tech industry and the former Editor-in-Chief at Tech Report. With a laser focus on tech product reviews, Wasson's expertise shines in evaluating CPUs and graphics cards, and much more.

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