Review – Dell Axim X51v

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This is a review of the Dell Axim X51v. The X51 is very similar, with less memory, QVGA instead of VGA display, lack of Intel video card and different wireless options.

For nearly a year, Dell’s Axim X50v has reigned supreme as the most powerful and affordable high-end Pocket PC on the market. Now, Dell has updated their existing design with more memory and Microsoft’s latest mobile operating system. Enter the Dell Axim X51 and X51v.

Design & Construction

Other than coming with Windows Mobile 5, and a substantially increased amount of flash memory, the X51v is virtually indistinguishable from its predecessor. The only way to tell by looking at their casings is to check the bottom front, where the model number is silkscreened onto the bezel. Otherwise, you’d never know the difference without turning it on.

This isn’t the first time that Dell has produced new hardware in an identical shell. The X3 and X30 lines were physically identical, but contained radically different hardware. The X51 is a much less drastic upgrade, but no less physically identical.

For those not already familiar with the X50 family, the casing is primarily black plastic, with rubberized trim on the back and a silver stripe along the front edge for flair. The curvy design minimizes the feel of size in the hand, and provides for very comfortable grip. Four application buttons sit on the front of the device, with two more on the left side. Also on the left are the lanyard hook, and the lock switch, which I’ll get to in a minute.

Only having four front application buttons does make using Windows Mobile 5’s one-handed navigation a little tricky, as it would require that users surrender all their main buttons if they want full navigation. It’s partly a limitation of the existing design, since newer models explicitly intended for WM5 usually have dedicated soft keys, and partly the result of the Axim not being a phone, resulting in one-handed navigation being seen as being less crucial.

The lock switch, when slid upward, prevents the Axim from receiving any input from its controls. The touchscreen, the application buttons, even the power button all cease to function. Slide the switch back down, and everything is fine again. It’s convenient for some uses where you may want to keep the Axim turned off, or keep it on without the risk of bumping the touchscreen. The only catch is that if you forget the lock switch is on, you may suddenly start wondering why your Axim isn’t working.

Top side are the expansion slots, CompactFlash and SDIO; the headphone jack; IR port; and stylus.

Having had an identical device for almost a year offers me a somewhat rare opportunity to take a look at how the X51 would hold up over the long term, even though it’s just been released. Despite 11 months of constant use, my X50v has taken only a few minor scuffs and marks, with no real deterioration or build problems. The credit here properly belongs to the Axim’s contracted manufacturer, HTC, a company which is famed for both its designs and its quality. Like their other devices, the Axims are built to last.

I can’t argue with the design of the X51v. I’ve always felt that the X50v is by far one of the best designed PocketPCs available. It’s sleek, feels good in the hand, and it’s visually appealing.

There are a couple of little things I’d like to see corrected. I’ve said it before, and I’ll say it again–the X51v lacks a jog dial. I’m certainly not the only person who misses this, so I fully intend to keep needling Dell until I get an X51v form-factor with an X30 jog dial. Likewise, I will continue my call for a return to the classic one-piece Axim batteries, as seen on the X5 and X3/X30–I much prefer a design that doesn’t require a battery cover.

As an interesting side note, the X51 and X51v are Dell’s first certifiably lead-free products. When they talked about this during our briefing call, mentioning how they had gotten all the lead out of the old X50 design, I confess that I cast a suspicious look down at the pocket my X50v was riding in. Fortunately, when asked, they explained that there hadn’t been very much lead at all in their previous devices, but that the X51s were the first to be certified. As it happens, the reason that the company went the extra mile in lead removal is because of new European rules which state that by a set point in 2006, any new devices imported into the EU must be certified lead-free.

The X51v comes with all the same standard equipment as the X50v–a simple & durable USB cradle with a slot for charging a second battery, microfiber slip case, AC adapter, etcetera. New to the X51 line, though, is an expanded range of bundled applications. Normally Dell skimps on the bundled apps, but this time for whatever reason they got a bit more generous, including full versions of Resco Picture Viewer, Geo Rally 3D, Toy Golf 3D, and Battery Pack Lite, as well as trial version of over a dozen more programs such as Resco File Explorer and Virtual Pool Mobile.



Processor: 624 MHz Intel XScale PXA270 with WMMX
Operating System: Windows Mobile 5.0
Display: 3.7 inch 480 x 640 VGA screen; Intel Marathon 2700G graphics accelerator with 16 MB video RAM; VGA output

64 MB RAM; 256 MB flash ROM (195 MB available)

Size & Weight 4.68″ x 2.87″ x 0.629″, 172 grams (6.06 ounces)

CompactFlash Type 2 and SDIO slots


36-pin connector, standard USB cradle


Integrated Bluetooth 1.2 and 802.11b WiFi


Internal monaural speaker; microphone; 3.5mm headphone/headset jack

Battery: Standard 3.7 volt, 1100 milliamp-hour Lithium-Ion battery; optional 2200 mAh LiIon extended battery

6 remappable application buttons; 5-way directional pad; touchscreen


Windows Media Player 10, 802.1x security client, bundled applications


Consumer IR, lock switch



The X51v is driven by the reigning champion of the handheld computing space, the 624 MHz Intel XScale PXA270. Despite being relatively old, having been in service for some 18 months, it’s still the fastest processor available on any handheld.

While performance wasn’t vastly different from the X51v’s predecessor, there were a few surprises. It’s common knowledge that current VGA PocketPCs’ performance suffers in comparison to QVGA devices. Having four times as many pixels to push around led to VGA models being noticibly slower in bringing up menus, loading icons, and in other graphically oriented tasks.

WM5 brings VGA performance into line with non-VGA devices. Screen redraws are much snappier, without the VGA induced lag. Icons and menus load quickly, and there’s a perceptible difference in response compared to the X50v.

Unfortunately, the benchmarks can’t quite bear this out. Our preferred general benchmarking tool, Spb Benchmark, doesn’t play well with Windows Mobile 5. A number of its tests failed due to changes in WM5’s internal structure, making even a partial set of benchmarks impossible.

WM5’s move to flash memory as the Storage medium of choice has provoked concerns about performance from some users. Flash memory is slower than pure RAM, so it was an open question whether the switch would cause slowdowns. The answer is no. While there may be some performance overhead that may be noticible by a few ultra-hardcore users, for the most part the transition to flash has gone very smoothly. Reading and writing is fast, an average of 25 times faster than the flash memory on the Axim X50v. How much of this is a real speed increase, and how much is WM5’s improved handling of flash, is unknown, but the bottom line is this: performance doesn’t suffer from the flash memory. Applications perform every bit as well as on pure RAM devices.

Average read speed:

Average write speed:

 8000 KBytes per second

2500 KBytes per second

Overall I would say that performance-wise, WM5 on the X51v feels very much like WM2003SE on a QVGA device. It’s reasonably fast, has no particular slowdowns, and jumps though its hoops in good form.


Operating System

The X51 is Dell’s first Pocket to feature Microsoft’s newest operating system, Windows Mobile 5. For an in-depth analysis of WM5 running on the X51v, check out our full review, available here.

Dell’s own additions to the OS are much the same as on previous Axims. Included in the ROM are the following applications:

Odyssey Client, which is a WiFi security and authentication program supporting WEP, 802.1x, EAP, PEAP, and other wireless encryption and security standards.

Data Backup, a simple application for backing up data to, and restoring it from, a memory card. Data Backup allows the user to back up all data on the device, or to selectively backup some or all PIM data (Calendar, contacts, email, etcetera).

Switcher Bar, a task switcher utility for moving between open applications, as well as accessing the battery meter and backlight control.

One thing that must be noted concerns the Dell backup application. Data Backup will not recognize or use backups made from prior OS versions, making it impossible to simply copy over all your files and programs. This is hardly a surprise, since a new OS usually makes significant changes to its internal structure, and restoring a backup from an old OS could end up causing malfunctions, eventually requiring a hard reset and reinstall of all programs anyway. However, not even PIM data alone can be restored, despite the relative simplicity and noninvasiveness of this option. The only way to restore your files and data to the device is by syncing it, then proceeding with a complete reinstall.



The 3.7 inch VGA screen in the X51v is largely indistinguishable from the X50v’s display, right down to the brightness settings. Color quality is very good. While it’s not the most vivid display available, you’ll likely never notice a difference unless you put it next to something spectacular. Brightness is past excellent. I’ve almost always run my X50v on the absolute lowest brightness setting, because anything more was simply overkill. The X51v is identical. The only time that brightness becomes a problem in my view is in total darkness, when the screen can actually be too bright.

If you read our review of the Axim X50v, you’ll recall that we had some difficulty performing benchmarks on its graphic systems. This was the result of Spb Benchmark not being properly equipped to test a VGA device, let alone take full advantage of the X50v’s Intel 2700G video chip. Fortunately, that’s not a problem this time around. Dell was kind enough to supply us with a copy of Futuremark’s SPmark ’04 mobile benchmark tool.

SPmark is a full OpenGL ES 3D benchmark, capable of giving the 2700G a real workout. Upon firing it up and starting the “High quality” rendering test, I couldn’t help but be impressed. The graphics were extremely vivid, despite stuttering on the most detailed parts. On the “Low quality” setting, the display was a little less impressive in detail, but smooth as silk.

SPmark ’04 results:

Low detail

High detail

26.0 Frames per second

8.9 Frames per second

The advantages of the 2700G don’t end with 3D performance. It also allows for MPEG1/MPEG4 hardware video decoding at bitrates up to 4 Mbits per second. In English, the 2700G lets you play DVD quality video at full speed without taxing the main processor. Last but not least, the 2700G also provides output to an external display via an optional VGA adapter cable. This means that you can hook the X51v up to an external monitor or VGA-equipped television to show pictures, play games, type, watch video, or surf the web.



The X51v is overflowing with memory. Dell has doubled the amount of internal flash memory to 256 MB. Between this, and the new memory system used by Windows Mobile 5, you’ll almost never have to worry about running out of memory again.

Before delving into the technical details, it’s handy to know a couple of basic points. “Storage memory” acts like a desktop’s hard drive, the area where you keep files and programs. “Program memory” is like a desktop’s RAM, and is used by active programs.

The newly upgraded 256 MB of flash memory in the X51v forms the biggest change from the Axim X50v. Under WM5, this area houses both the operating system, and the device’s primary storage. Minus room for the OS, you’re left with a whopping 195 MB of Storage memory on the X51v.

Both of the two lower models in the X51 series have 128 MB flash memory. This is the same as the X50 series for the mid-range device, but double what the low-end received last time around, a very fair upgrade.

Prior to Windows Mobile 5, the primary storage area of a PocketPC was a chunk of the device’s RAM. Applications could be installed on memory cards or elsewhere, but the RAM served as the home of Windows files and other essentials. Since RAM required power all the time in order to maintain its contents, increasing available memory also meant significantly increasing the battery drain. Now all those files and programs have been moved into flash, storage memory can be increased without a battery life penalty. The X51v has 256 MB internal flash, but it wouldn’t be impossible to build a device with 512 MB, 1 GB, or even more.

Besides pure speed, flash memory does have one significant drawback over RAM. After a certain number of rewrites, flash memory begins to degrade and show errors. Fortunately, the number of rewrites is quite high, anywhere from 100,000 to 1 million writes per sector. So while the flash in the X51v will eventually deteriorate with continual use, it’s not likely to happen before the march of technology turns it into a doorstop anyway.

Thanks to the new memory arrangement, Storage memory isn’t the only thing that gets a boost. On prior Windows OSes, the system’s RAM was divided more or less evenly between Storage memory and program memory. Hence, a Pocket PC that had 64 MB of actual RAM effectively used only 32 MB of it for program memory. To get a full 64 MB for running programs, you needed to buy a 128 MB PocketPC.

Under WM5, all of a device’s RAM, in this case the full 64 MB, is used for running programs. This makes a 64 MB WM5 device the equivalent in program memory of a 128 MB WM2003SE or earlier model.

If all this talk of storage, program memory, and etcetera has you confused, don’t worry. The new system used by WM5 is actually much simpler than its predecessor. The X51v’s main storage, where all of its files and programs are kept, is flash memory. This works more or less like a desktop hard drive, and retains its contents even if your battery dies. The RAM, like the RAM on a desktop, is used only for running active programs, and doesn’t get maintained if your battery dies.

The new handling of RAM does mean that a fully drained battery can still result in some data loss for open documents and programs, because the RAM isn’t backed up against loss. It’s equivalent to having your PC reboot–everything returns to the way it was the last time you started it up. Likewise, any time you change your battery, no matter how fast you do it, you’ll end up with a soft-reset. I’m not particularly happy about this, since it’s very annoying when you have to wait for your handheld to reboot following a quick battery swap, but that’s the way it is.


Size & Weight

One weight class above the ultra-thin devices, the X51v sits on a dividing line for bulk. Not too large for comfort, not too small to fit its features, it matches almost exactly the other “small” contenders in the VGA PocketPC market. I find the size and weight quite satisfactory, providing small size and a decent heft.



The X51 line features both CompactFlash and SDIO expansion slots, standard in a high-end PocketPC. This allows for a wide range of peripherals including GPS receivers, wireless modems, barcode readers, and more, as well as expansion cards providing gigabytes of memory.



One major benefit of not changing device form-factors is that you get to use all your old toys. In this case, the X51v is compatible with anything that the X50v was, including batteries, styluses, cables, cradles, right along to the VGA output cable.



The X51’s Bluetooth and WiFi provide all the medium-range wireless connectivity you could want. A Bluetooth link to a data-enabled mobile phone, or a WiFi connection to a base station, can give you access just about anywhere you go.

I’ve never been entirely happy with the X50v’s WiFi performance, and the X51v is no exception. Range is less than what I would consider ideal under most circumstances. Still, it speed and range was acceptable when provided with a good enough signal.

Someday I’d like to see an external antenna jack available on WiFi enabled devices, situated under a little rubber cap on the back the way that some cell phones’ antenna jacks are.



The X51v retains all the sound hardware of the X50v, including the headphone jack and microphone, wired headset support, Bluetooth headset profile, and the WM8750 audio processor. All this tallies up to a machine that’s equally capable as an MP3 player, a VOIP phone, or a portable audio recorder.



It’s no secret that the biggest failing of the Axim X50v has always been the battery. While adequate for most usage, battery life dropped precipitously as soon as you started to take real advantage of the X50v’s high-end functions. While the capacity of the battery in the X51s has not changed, total battery life has improved significantly. Part of this is attributable to increases in efficiency, but the largest share of the credit belongs to Windows Mobile 5.0.

A device’s RAM requires continuous power to maintain its contents. When PocketPCs stored their most critical data in RAM, it was neccessary to insure that a user who ran the battery down to zero didn’t trigger a hard reset. Therefore, one of Microsoft’s design mandates for its licensees was that every PocketPC had to keep a power reserve, enough to keep the memory intact for 72 hours after the battery “died.” Called the “72 hour rule,” this would allow someone to go all weekend with a dead battery, then charge up again when they had the opportunity, without losing their data.

However, this buffer space exacted a price in performance. Because of the need to reserve power, users were getting less than the full capacity of their batteries. When the battery meter hit 0%, the battery still contained 15%, 25%, maybe even 50% of its original charge, kept away from the user to feed the RAM.

Skip forward to today. Starting with WM5, all essential data is in flash memory, which requires no power to maintain its contents. Thus, the 72 hour battery reserve is no longer relevant, and the user can run their battery clear down to empty without worrying about a hard-reset.

To give an accurate picture of the X51v’s battery life, and how it differs from the X50v, I’ve put together a table comparing scores of both the X50v and X51v, on both standard and extended batteries, as well as the X51v’s primary competitor, the iPaq hx4700. In all wireless tests, both Bluetooth and WiFi were active until the device shut down. Processor tests simulate playing of a high-bitrate, DVD quality video. Battery tests with the 2200 mAh extended battery resulted in just over 2x the runtime of the 1100 mAh batteries in each permutation.

  Axim X50v, 1100 mAh Axim X51v, 1100 mAh iPaq hx4700, 1800 mAh
Backlight at minimum, processor active: 4 hours, 10 minutes 6 hours, 20 minutes N/A
Backlight at 50%, processor active: 3 hours, 32 minutes 4 hours, 18 minutes

6 hours, 5 minutes

Backlight at maximum, processor active: 2 hours, 42 minutes 3 hours, 36 minutes 4 hours, 18 minutes
Backlight at minimum, wireless active: 5 hours, 12 minutes 6 hours, 48 minutes N/A
Backlight at 50%, wireless active: 3 hours, 50 minutes 5 hours, 35 minutes 3 hours, 33 minutes
Backlight at Maximum, wireless active: 2 hours, 54 minutes 4 hours, 11 minutes 2 hours, 47 minutes

According to Dell’s official briefing on the X51, the increase in battery life should be around 15% over the same model X50. I found it to be higher in most scenarios, around a 25% improvement over a similarly equpped X50v. This is quite impressive given that the battery capacity hasn’t changed in the least. While it’s still not the longest lived model on the market, the X51v goes a long way towards eliminating battery life as a negative of VGA devices.



While the X51v is in some ways the least impressive upgrade that Dell has ever made, from another perspective it makes sense. The X50v has for almost a year been the king of the traditional handheld, the most affordable and flexible high-end device on the market. Even now, it’s hard to trump. The X51v provides a reasonable update, something to keep the model current without trying to fix something that’s not broken. I doubt that many X50v users will want to bother with upgrading, but the X51v offers appealing enticements to new buyers. It’s well designed, well built, and is loaded to the hilt with features.


  • Windows Mobile 5.0
  • Large, fast flash memory
  • Improved battery life
  • CompactFlash & SDIO slots
  • Bluetooth & WiFi
  • VGA screen
  • Advanced graphics chip
  • Fully compatible with X50 models


  • Unoriginal, if still stylish, design
  • No jog dial
  • Only four front buttons
  • Temporary WM5 glitches
  • Soft reset on battery swap

Bottom Line:

Not a huge upgrade from the X50v, but a decent improvement to an already excellent device.

Pricing and Availability



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