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Siemens SX66 GSM Pocket PC Phone

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Review posted March 22, 2005 by Lisa Gade, Editor in Chief

Check out the Cingular 8125 (HTC Wizard) which replaces the SX66 on Cingular

You can never have too much of a good thing. The Siemens SX66 offered by Cingular in the US is one of the many HTC Blue Angel variants sold around the world by several carriers and wireless phone manufacturers. These variants are sold as the XDA III, MDA III, iMate PDA2K, Audiovox PPC-6601 and Audiovox XV6600. The first three are GSM models sold overseas only, and the last two are CDMA versions offered by Sprint and Verizon Wireless respectively. While the GSM models have integrated WiFi 802.11b wireless networking and the not-too-speedy GPRS for data, the CDMA models lack WiFi but run on Sprint and Verizon's faster 1xRTT wireless data networks. Otherwise the models are identical, and you'll notice a great deal of overlap between our review of the Audiovox PPC-6601 and the Siemens SX66 as they are identical in all respects save network (GSM vs. CDMA), presence of integrated WiFi and cellular wireless data connection technology. The device's biggest claim to fame is its slide out QWERTY keyboard that is hidden until you need it.


Siemens SX66
back of SX66


The Blue Angel is HTC's third generation Pocket PC phone. HTC designs and/or manufactures many fine PDAs and smartphones, including several HP iPAQ Pocket PCs, the Treo 650 and the Audiovox SMT5600 Windows Mobile Smartphone. They are also responsible for the well-received XDA II which was never offered in the US but was sold here by importers. The XDA II was the first truly powerful and feature-packed Pocket PC phone, and it set the bar for high end PPC phones. In the US, Siemens sold the first generation XDA as the SX56, and they now bring us the third generation Siemens SX66.

The SX66 is a full-featured, powerful Pocket PC phone that looks and acts like a Pocket PC and doubles as a cell phone. By phone standards this is a large beast, but by Pocket PC standards it is of average size, which can be said of most Pocket PC Phone Edition devices. It runs the Windows Mobile 2003 Second Edition operating system with support for both portrait and landscape orientations, has a fast 400MHz Intel Xscale processor and a whopping 128 megs of RAM. The SX66 has integrated Bluetooth and WiFi 802.11b and an SD slot for expansion. While Pocket PC phones lagged behind their non-phone brethren in the first few years, the XDA II and now the XDA III (Siemens SX66) give most Pocket PCs a run for the money when it comes to power and expandability.

The device has a quad band (850/900/1800/1900MHz) GSM radio that will work anywhere in the world where GSM service is available and has GPRS for data. Though the device is sold only through Cingular it is unlocked and works with other carriers' SIMs.


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Design and Ergonomics

Pocket PC phones target convergence users who wish to combine a PDA and mobile phone rather than carry two separate devices. Though the SX66 is larger than a cell phone, it is a more compact and convenient solution for many folks who currently carry two devices. It may seem strange to hold a PDA to your head, but in practice it's neither that strange nor uncomfortable. The top speaker and bottom mic are perfectly positioned for phone calls, and the unit is easier to hold than current miniaturized cell phones. The drawback is that the device is heavier than a traditional mobile phone and you may get some facial oils on the display which may look unsightly but won't harm the LCD. Of course, you can use the included stereo earbud headset or an optional Bluetooth headset and thus rarely have the device against your face.

The Siemens SX66 is the size of a large Pocket PC, and has pleasing curves that feel good in the hand. The unit is attractive and modern looking with a silver front bezel and black plastic back. The most striking feature is the phone's sliding design: slide the back half downward to reveal a QWERTY thumb keyboard with backlighting.

open with keyboard showing
back view

side view of Siemens SX66


Views of the phone with the slider open: front, back and side.


Buttons abound on the SX66, unlike most Pocket PC phones. While most PPC phones have only call send and end buttons and two application buttons on the front face, this unit adds 4 thin horizontal application buttons just below the display. This is great news for gamers, who often need several applications buttons for games and were left wanting with other PPC phones. The unit has a rounded rectangular direction pad that moves easily in all directions, supports diagonals and has a center action button. The speaker is located above the display and the mic is at the bottom of the phone, which is standard for units that double as phones.

On the left side you'll find the voice recorder button, volume slider, Windows Media Player button and the IR window. As with all Pocket PCs, you can re-assign different applications to all buttons except the dedicated call send and end buttons. The stereo 2.5mm headset jack is located on top, as are the SD slot and power button. The stylus lives in a silo on the top right and there are no buttons on the right side of the unit. As you'd expect, the sync/charge connector is located on the bottom. The user-replaceable Lithium Ion battery is inset into the back of the phone and sits flush. The battery door is integrated into the battery.

Horsepower and Performance

While not the fastest Pocket PC on the market, the Siemens SX66 is currently one of the fastest Pocket PC phones thanks to its state-of-the-art 400MHz Intel PXA263 XScale processor (the Samsung i730 running at 520 MHz is the fastest). Those of you who were wishing for an even faster processor should keep in mind that battery life suffers as processor speed increases. The SX66 is fast enough to please demanding users, gamers and avid video watchers. It has a generous 128 megs of RAM and 43.26 megs of Flash ROM available for program and data storage. That's considerably more Flash ROM than the Sprint version of this phone which has 14.57 megs, but the same amount of RAM. The unit uses an ATI graphics processor which gives good performance in gaming and video playback. All applications responded quickly and games run quite well on this device. It is a power user's dream to be sure. The SX66 has been very stable for us in three weeks of testing, and has proved a reliable companion on the road. For expansion, the unit has an SD slot that supports SDIO Now! This means you can use the slot for SD memory cards as well as networking cards, GPS and modems, though you generally won't be needing additional networking on this wireless jack of all trades.

Phone Features and Reception

The SX66 is a GSM device sold by Cingular in the US (for the first few months it was sold unlocked but it is now sold locked). What does locked mean? If a phone is locked, it can only be used with a SIM from the carrier who sold you the phone, and not a competing carrier's SIM. The Siemens is a world phone that supports all GSM bands (850/900/1800/1900MHz) so you can use it anywhere in the world where GSM service is available. Signal strength on Cingular in the San Francisco Bay Area has been good and just above the middle of the pack for a GSM phone. Both incoming and outgoing voice volume and clarity are excellent. In fact, the Blue Angel has a louder earpiece that most other GSM phones currently on the market.

Like all Pocket PC phones, the Siemens has a large on-screen dialer application with numbers that are large enough to dial using a finger. This screen has a call send/end button, a speed dial button, call history button and a hold button that appears when in a call. You can mute a call by tapping on the mic icon in the task bar, bring up the address book by tapping the Contacts icon and open Notes if you wish to jot down notes or drawings when in a call. You need not tap out phone numbers using the on-screen dialer, and instead can make calls with one press using the speed dial function. Speed dial can hold up to 99 numbers (1 is assigned to voicemail), and if you wish to use voice dialing you can purchase Microsoft's Voice Command.

All Pocket PC Phones have flight mode, and the SX66 is no exception. Simply tap on the signal strength meter on the menu bar and select flight mode to turn off all wireless features. You can still use the PDA functions when the device is in flight mode. The device has a speakerphone which is quite loud. To activate it, press and hold the call send button for a second or two when already in a call. If you prefer a headset, the device will automatically route calls to the included stereo earbud headset when attached, and mute MP3 or video playback when a call comes in. You may also use Bluetooth headsets with the device, though voice dialing is only supported when using the phone or a wired headset, not a Bluetooth headset (this is currently true of all Pocket PC phones except the HP iPAQ 6315).

The phone has class 10 GPRS for data which provides throughput around 45k on average in our area. We wish it had EDGE (so far a no-show on Windows Mobile phones) but alas it does not. Given the screen resolution and rendering capabilities of Pocket Internet Explorer and third party web browsers, a faster data connection would be ideal to speed up page load times which can approach 20 seconds for a desktop optimized web site. Those who are not tied to GSM but love this phone might want to consider the Audiovox CDMA versions sold by Sprint and Verizon, both of which offer 1xRTT for data with an average throughput of 95k. Verizon's EV-DO 3G service is already available in many US cities and that will get you 200k or better and feels like WiFi in terms of download speeds. Speaking of WiFi, the Siemens has 802.11b which means you can enjoy very fast data speeds when near an access point or public hotspot while the CDMA versions lack WiFi.


Since GPRS speeds won't knock your socks off, the SX66 has WiFi which is the de facto standard for super-fast data connections on PDAs. Browsing the web and downloading email attachments over WiFi is a pleasure! To configure and manage your WiFi connections you'll use the SX66 Wireless Manager application. You can easily launch the application from the Today Screen's taskbar, or from the Programs group. If you launch Wireless Manager from Programs, you'll also be able to turn on and off the GPRS and Bluetooth connections, manage existing connections and work with 802.11b connections. When you tap on the antenna tower icon in the taskbar, you'll go directly to the WiFi manager screen. Here you'll turn the WiFi radio on or off, and see detailed status pertaining to your current connection. You can also manage power saving settings using a slider that goes from Best Performance to Best Battery, and optionally set a timeout to turn off the WiFi radio if the connection is inactive after a user-specified period of time. Wireless manager also takes care of LEAP connection settings as needed.

To create a new WiFi connection, you'll use the Windows Mobile Connection Manager which is a part of the OS. Connection Manager detects and alerts you to available access points and walks you through connecting to them. The device supports 64 and 128 bit WEP encryption and secure certificates. We found that WiFi connections were reliable using a variety of access points including those using WEP encryption and had good range even when set to use the most conservative power settings.


The SX66 uses excellent Broadcom (formerly Widcomm) v. 1.0.0 Build 2400 Bluetooth stack and its associated user-friendly software along with a good set of profiles. The unit has profiles for FTP, information exchange, serial port, personal network server, dial up networking server (DUN), ActiveSync, Audio Gateway and Handsfree for headsets. We tested the phone with a variety of headsets, including the Motorola HS820, Bluespoon AX and the Plantronics M3500 and found that the SX66 has just passable range compared to dedicated phones made by Nokia and Sony Ericsson. Handsfree features such as last number redial from the headset, automatic call transfer and mute worked just fine, but we never got system sounds to pipe through to the headset despite the working Audio Gateway profile. Note that like most Pocket PC phones the SX66 does not support voice dialing through a Bluetooth headset.

size comparison

Above, a smartphone gathering. Comparing the HP iPAQ 6315, palmOne Treo 650, Siemens SX66 and the Audiovox SMT5600 (C500).


What good is a powerful mobile email tool without a keyboard? Don't want to carry an accessory keyboard? Siemens has the answer: the slider keyboard. When you need it, slide the back half of the PDA down to reveal a QWERTY thumb keyboard. Though the keys are only slightly raised and have little tactile feedback, the keyboard is surprisingly easy to use. The keys are curved in a radial pattern which provides for a more ergonomic typing experience and allows for more space between the keys. Thanks to the generous key spacing and grippy key surface, I found it easier to type on the SX66 than the venerable Treo 650; but keep in mind that such things are somewhat a matter of personal taste.

The keys are backlit in blue and are easy to see in the dark but thankfully aren't blindingly bright. The embedded number keys and Fn key are outlined in red while the rest of the keys are outlined in black. This makes it easy to punch in a phone number, and when you're in the phone dialer screen, the unit automatically switches to the embedded number keys which are superimposed on the letter keys. The Siemens has a Settings applet where you can enable/disable keyboard backlighting, specify how long it stays on after a key is pressed (2, 4, 6, 8 or 10 seconds), and set repeat rate.

Display, Gaming and Multimedia

Like the other Blue Angel variants, the Siemens SX66 has a very good 3.5" transflective display that's quite bright, sharp and has good color saturation and balance. The screen is better than the HP iPAQ 6315's and on par with the Treo 650 and Samsung i700 Pocket PC phone.

Sound volume in call through the speakerphone and system sounds are plenty loud on the built-in speaker. Like all Pocket PCs, the SX66 can play MP3s using the included Windows Media Player 9. For best sound you'll want to use the included stereo headset rather than the integrated mono speaker.

Games work well on the SX66, equaling the performance of the XDA II and the SX66's kissing cousin, the Audiovox PPC-6601. The Blue Angel offers a better gaming experience than most other Pocket PC phones thanks to the addition of more application buttons which can be used in game. We tested a variety of demanding, popular current games and all played well.

The unit makes a great portable video player, but do get yourself a fast SD card to store those large video files! Videos played with Windows Media player, Pocket TV and BetaPlayer were a pleasure to watch.

BetaPlayer is an extremely fast open source free video player that supports MPEG1, DivX, AVI, ASF and WMV files. BetaPlayer played back "The Chosen", (a neat BMW flick with Clive Owen) which is a 4:26 minute long, 10 meg MPEG1 file recorded at 320 x 240, 308 kb/s, with benchmarks of:
Average speed: 362.14%
Bench Frame Rate: 86.91
Bench. Data Rate: 1.1 Mbit/s
Orig. Frame Rate: 24fps
Orig. Data Rate: 310 kbit/s

Those are very good results, and a hair better than the Audiovox PPC-6601, which may have more to do with continuing improvements in BetaPlayer than the device.


Since they share the same core, the SX66 and other variants such as the Audiovox PPC-6601 fare nearly identically on benchmarks and video playback. If you've used an XDA II, you will find little difference in overall performance since the models share the same processor and memory architecture. In fact, benchmark numbers are extremely close, with the XDA II having a tiny (and we mean tiny) edge in some numbers, likely the result of software installed by the respective operators. Having owned the XDA II, I can tell you the Siemens SX66 feels identical in terms of performance and runs the same applications well, including games. How does it compare to the original XDA (T-Mobile Pocket PC Phone) and the iPAQ 6315? It is much faster.

Benchmark Results

HP iPAQ 6315
(2003, 168MHz Ti)
Samsung i730
(520 MHz XScale)

Audiovox PPC-6601
(2003 SE, 400MHz X-Scale)

Siemens SX66
Spb Benchmark index
CPU index
File system index
Graphics index
Platform index
Write 1 MB file (KB/sec)
Read 1 MB file (MB/sec)
Copy 1 MB file (KB/sec)
Write 10 KB x 100 files (KB/sec)
Read 10 KB x 100 files (MB/sec)
Copy 10 KB x 100 files (KB/sec)
Directory list of 2000 files (thousands of files/sec)
Internal database read (records/sec)
Graphics test: DDB BitBlt (frames/sec)
Graphics test: DIB BitBlt (frames/sec)
Graphics test: GAPI BitBlt (frames/sec)
Pocket Word document open (KB/sec)
Pocket Internet Explorer HTML load (KB/sec)
Pocket Internet Explorer JPEG load (KB/sec)
File Explorer large folder list (files/sec)
Compress 1 MB file using ZIP (KB/sec)
Decompress 1024x768 JPEG file (KB/sec)
Arkaball frames per second (frames/sec)
CPU test: Whetstones MFLOPS (Mop/sec)
CPU test: Whetstones MOPS (Mop/sec)
CPU test: Whetstones MWIPS (Mop/sec)
Memory test: copy 1 MB using memcpy (MB/sec)

Battery Life

The Siemens SX66 has a 1490 mAh Lithium Ion Polymer rechargeable battery, which is a decent capacity for a phone with two forms of wireless and a fast processor. It also represents an improvement over the XDA II which had a 1,200 mAh battery that could generally make it through one day with average use, but sometimes less. The Siemens did make it through the day for us with power to spare when not using WiFi. If you use the device to talk for 30 minutes, surf for 30 minutes per day over GPRS, check email 10 times per day, access PIM info (calendar, tasks, contacts) several times per day and play games for 30 minutes per day, you should easily make it through the day. WiFi decreases runtimes on all PDAs, and you'll get about three hours of actual use when using WiFi 802.11b. The battery is user replaceable which means you can easily swap in a spare if you need more juice.

The phone has a Button Lock feature which you can enable to prevent accidental button presses from turning on the unit. When enabled via Settings -> System -> Button Lock, only the power button will turn on the unit. None of the Blue Angel variants, including the SX66, have power settings which allow you to select a lower CPU setting to save power.

The phone comes with a cradle that allows you to both sync and charge the device and it has a second slot to charge a spare battery. When traveling you need not bring the cradle to charge the device since the included charger can plug directly into the phone using a small included dongle adapter.


Like all Pocket PCs running Windows Mobile 2003, Pocket versions of Word, Excel, Internet Explorer, Outlook and handwriting recognition are pre-installed in ROM. Other pre-installed Microsoft apps include Pictures, Terminal Services, MSN Messenger, Solitaire, Jawbreaker, ActiveSync and Calculator. The unit comes with Windows Media Player 9 for MP3 and WMV/ASF movie playback.

Siemens and Cingular value-added software pre-installed in ROM includes Photo Contacts, Express Mail, SIM Manager, Wireless Manager (Wi-Fi manager), Wireless Modem (allows you to use the phone as a modem for a PC via cabled, IR or Bluetooth connections), Java MIDlet Manager by the Tao Group, xBackup which allows you to back up all or just PIM data to Flash ROM or an SD card, Enroller (certificate enroller), and Album (an image viewer formerly known as IA Album).


This flagship Pocket PC phone allows you to take the office, web and email on the road. It's powerful, attractive and the slider keyboard makes it a good email solution. This is a well-made device with HTC's excellent heritage behind it, and will make a wonderful mobile office on the road. If you're a Pocket PC user who prefers to carry one device and wants easy data connectivity, the Siemens SX66 is a superb choice.

Pro: Innovating sliding keyboard design that's not merely clever, it's very useful. Fast performance. Has GPRS, WiFi and Bluetooth. Well made and attractive. Good capacity battery. Plenty of application buttons for gamers.

Con: No EDGE or 3G, and a Pocket PC begs for faster data connection speeds than GPRS provides. Like all Pocket PC phones, it's much larger than a standard cell phone. Again, like all Pocket PC phones and unlike standard cell phones, all data will be lost if the battery runs completely down. Fortunately a good backup application is included. Battery life is just OK.

Web Sites:,

Price: Approx. $549 with 2 year contract

Shopping: Where to Buy



Display: Transflective TFT color LCD, 64K colors. Screen Size Diag: 3.5", Resolution: 240 x 320.

Battery: Lithium Ion Polymer rechargeable. Battery is user replaceable. 1490 mA. Claimed talk time: 4 hours, claimed standby: 200 hours.

Performance: Intel XScale PXA 263 400 MHz processor. 128 MB built-in RAM. 64 MB Flash ROM with 14.57 megs available for your use.

Size: 4.9 x 2.75 x .74 inches. Weight: 7.4 ounces.

Audio: Built in speaker, mic and 2.5mm stereo headset jack. Stereo earbud headset included. Voice Recorder and Windows Pocket Media Player 9 included for your MP3 pleasure.

Networking: GSM quad band phone 850/900/1800/1900MHz with GPRS class 10 for data. Integrated Bluetooth and WiFi 802.11b. Standard IR.

Software: Windows Mobile 2003 SE for Pocket PC Phone operating system. Microsoft Pocket Office suite including Pocket Word, Excel, Internet Explorer and Outlook. Also, Terminal Services, MSN Instant Messenger for Pocket PC and Voice Recorder, Solitaire, Jawbreaker as well as handwriting recognition. 3rd party and HTC software: Album (image viewer), xBackup, Photo Contacts, Java MIDlet Manager, Wireless Manager (for Wi-Fi), Wireless Modem (allows you to use the phone as a modem for a PC over Bluetooth, IR, Serial or USB). ActiveSync 3.7.1 and Outlook 2002 for PCs included.

Expansion: 1 SD (Secure Digital) slot supporting SDIO and SDIO Now!.


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