First, let’s clarify the terminology. "Second-generation" refers to a combination of two factors. First, it’s the second or later Tablet PC developed by an OEM, taking advantage of lessons learned on their first model. Second, it uses the latest technology, for example, a Pentium M processor.

This article covers only "commercial" Tablet PCs, since selecting a rugged Tablet PC involves additional factors (such as evaluating and comparing environmental specifications) that are beyond the scope of this article. Tablet PCs from Getac, Intermec, Itronix, Kontron, Microslate, Motorola, Panasonic, Symbol, Walkabout and Xplore are therefore not considered.

The second step required to get down to a manageable subset of Tablet PCs is to eliminate those OEMs who don’t have a significant presence in the USA. This is justifiable both on an enterprise and individual-user basis mainly by the lack of pre- and post-sales support available on their products. Tablet PCs from Advueu (formerly TDV Vision), ECS (EliteGroup), FIC, LG, PaceBlade, Sotec and WintopUSA are therefore not considered.

The final step is to eliminate products in several special-case categories: (a) OEMs such as Dell who simply resell other OEMs’ Tablet PCs, (b) OEMs such as NEC who either haven’t developed a second generation or who have indicated to the author that they are planning to exit the Tablet PC business after their current model sells out, and (c) OEMs such as Clevo whose product isn’t actually a Tablet PC (i.e., it doesn’t run XP Tablet PC Edition). Tablet PCs from Cabin Five, Clevo, Dell, Eurocom, LEO Systems, NEC, Research Machines, Sharp, Time Education, Torspoal and Viglen are therefore not considered.

What’s left is a manageable list of 11 Tablet PCs from nine OEMs, as shown in Table 1. In the case of Gateway, only their convertible Tablet PC is considered, since their slate is a re-branded Motion Computing product. Averatec (formerly SOTEC America) is a special case – even though they are a new company and have limited support in the USA, their $1,350 C3500 Tablet PC sets an entirely new price benchmark in the market.

Table 1: Commercial Tablet PCs considered in this article.

The starting point in selecting a Tablet PC is determining if you want a slate or a convertible.  The answer depends on how you will use the device.  If you need instant access to a keyboard, you should buy a convertible.  If you want the thinnest and lightest Tablet PC, if most of your work can be accomplished with a pen (i.e., you're doing very little text entry) and you're willing to go through some extra trouble to use a keyboard, then you should buy a slate.  "Extra trouble" can include setting up an attachable keyboard, plugging in an external keyboard, setting up a separate stand to hold the Tablet PC on a desk, etc. However, be aware that most slates are purchased for use in vertical applications -- e.g., nurses accessing patient data, insurance adjusters estimating repair cost on a damaged car, pharmaceutical sales reps making presentation to MDs on the run, etc.  Very few "general-purpose users" purchase a slate because they're just not as convenient to use as a convertible with a standard notebook form-factor.

Selecting the most desirable screen size for your application is probably the second most important decision after choosing the form-factor. All slate Tablet PCs are either 10.4" or 12.1", in order to minimize the weight since slates are designed to be arm-carried while in use.  10.4" is a very small screen, so it's hard to take a full page of notes on it -- but it's very sharp at 123 dpi (dots [pixels] per inch).  The advantage of a 10.4" screen is the small size and weight of the system.  12.1" is easier to read because the fonts are larger, and it's and easier to take notes on, since it's a closer match to 8.5" x 11" paper – but the screen is slightly less sharp (more pixelated) at 106 dpi.

If you want a 14.1" Tablet PC, then you must buy a convertible.  There are only two 14.1" convertibles, Acer’s C300 and Gateway’s M275. The Acer C300 has substantial advantages over the Gateway M275, including a media bay, anti-shock hard drive mounting, larger battery, docking port and port replicator, Gigabit LAN, Bluetooth, automatic backlight light sensor, S-video port, four-way scroll button and a much more extensive software bundle. On the negative side, the Acer C300 is 0.5 pounds heavier and 23% larger in volume than the Gateway M275.

It's unlikely that the next generation of 10.4" and 12.1" Tablet PCs (expected in early 2005) will offer many more higher-resolution screens; XGA is likely to remain the standard resolution until 2007 (the approximate timeframe of Longhorn, the next major version of Windows).  In contrast, the next generation of 14.1" Tablet PCs are very likely to move up from XGA to SXGA or SXGA+ resolution, since that's where most standard 14.1" and 15" notebooks are headed.

Most Tablet PC screens have moderately wide viewing angles in landscape mode and very narrow viewing angles in portrait mode.  This means, for example, that to get a optimum view of an image or document in portrait mode, you must hold the Tablet PC at only one specific position or angle. This makes it relatively annoying to use.  Some of the newer Tablet PCs have all-direction wide-angle screens (160° in both landscape and portrait modes), which makes using a Tablet PC in portrait mode much easier. 

The only slates in Table 1 with wide-angle screens are the 10.4" HP TC1100 and the 12.1" Motion M1400.  The only convertible in Table 1 with a wide-angle screen is the 12.1" Averatec C3500.  It's unfortunate that the Toshiba M200 doesn’t have a wide-angle screen, because otherwise it's an excellent convertible Tablet PC.

It's very likely that many of the next generation of Tablet PCs (expected in early 2005) will offer wide-angle screens.  Microsoft is pushing the Tablet PC OEMs to include this feature in the next generation.  If wide-angle viewing in portrait mode is very important to you (i.e., if the majority of the software that you use runs mainly in portrait mode), consider waiting to purchase your Tablet PC until 2005.

The only commercial (non-rugged) Tablet PCs with outdoor-readable screens are the Motion M1400 and Fujitsu ST5000 slates.  If you don't need to use your Tablet PC outdoors in direct or indirect sunlight, then this specification doesn't matter very much.  It’s likely that more Tablet PCs will have outdoor-readable screens in the future, although the adoption rate won’t be as fast as wide-angle screens.

All 10.4" and 12.1" Tablet PCs except the 12.1" Averatec don't have internal optical drives.  This means that if you frequently need an optical drive (a CD-ROM, CD-RW or DVD), then you must carry and use an external drive -- along with possibly another AC adapter.  Both 14.1" Tablet PCs have an integrated optical drive; the drive in the Acer C300 is removable (it’s in a media bay).

All the latest generation of Tablet PCs use Intel’s Pentium M CPU (except the Averatec, which uses an AMD CPU).  Any product using the older Pentium III-M or the plain (not -M) Celeron is effectively obsolete.  The absolute minimum processor speed you should consider in a second-generation Tablet PC is 1.0 GHz.  The fastest Tablet PC on the market today is the Toshiba M200 at 2.0 GHz.  (According to Averatec, the C3500’s AMD Athlon XP-M 2200 CPU is roughly equivalent to a 1.3 GHz Pentium M.)  Some Tablet PCs offer a choice of several different speeds within the same series. For example, Gateway offers 1.5 GHz and 1.8 GHz models. 

What speed you should select depends on several factors, including (a) your personal need for speed (i.e., how used you are to using a >2 GHz desktop or full-size laptop), (b) your need for long battery life (for a given battery size, faster processors result in shorter battery life), and (c) your budget (faster processors are definitely more expensive, thanks to Intel's pricing model). In general, it will take longer for Tablet PCs with faster processors to begin to feel painfully slow in comparison to the latest super-fast systems. The author’s experience is that because of this "lifetime" factor, it’s nearly always worth getting the fastest processor you can afford.

Actually there are two different flavors of Pentium M.  The original version (130 nm process, 1.0 GHz to 1.7 GHz) is identified as just "Pentium M".  The newer version (90 nm process, 1.0 to 2.0 GHz) is identified with a model number, as shown in Table 2.

Table 2: Intel Pentium M model numbers vs. speed

Because of the new 90 nm process, the model-numbered Pentium M offers higher performance and lower power consumption (longer battery life) than the original Pentium M. When given a choice between the two CPUs (such as in the Toshiba M200), choose the model-numbered Pentium M.

There are also five models of Celeron M (900 MHz to 1.5 GHz), but it’s generally not a good idea to buy these, since their L2 cache size is only 25% of the Pentium M’s (512 KB vs. 2 MB), and they’re made with the older 130 nm process. All Pentium Ms and Celeron Ms use a 400 MHz front-side bus.

The best indicator of battery life is the battery size in watt-hours, since the internal electronics of most Tablet PCs are relatively similar.  The battery size of any portable computer can be calculated by multiplying the current rating of the battery in ampere-hours by the voltage rating in volts.  The result is watt-hours.  A few Tablet PC vendors give their battery size directly in watt-hours, such as Motion Computing (the M1400’s battery is specified as 40 watt-hours).  However, many Tablet PC vendors only specify the current rating (usually in milliampere-hours, equivalent to ampere-hours/1000), such as Toshiba (the M200 battery is specified as 4,400 milliampere hours).  Unfortunately, without knowing the voltage rating, this is a totally meaningless specification.  Looking at the actual battery (all Tablet PC batteries have their voltage rating on the label), or calling the vendor are typically the only ways to obtain this information.  The battery sizes of all the Tablet PCs in Table 1 are shown in Table 3, in order of increasing battery size.

Table 3: Tablet PC battery size in watt-hours

Many of the battery life specifications provided by the Tablet PC OEMs are relatively meaningless.  Often they are given as "up to X hours", which is based on impractical operating conditions such as minimum backlight brightness, no wireless usage, minimum HDD access, etc.  Estimating battery life from the battery size yields a more reliable estimate of battery life.  As a general approximation, the typical 10.4" or 12.1" Tablet PC uses around 12 watts per hour.  This means that a 40 watt-hour battery should last 40/12 = 3.3 hours.  (As confirmation, Mobile PC Magazine recently tested the Motion Computing M1400 and measured 3.2 hours of actual battery life.)  Note that the "12 watts per hour" figure will vary depending mostly on the backlight setting (+/- 1.5 watts), how heavily the CPU and HDD are used (+/- 1.0 watts), and how often the wireless LAN is used, (+/- 1.0 watts). For 14.1" Tablet PCs, use 16 watts per hour.

From the battery sizes listed in Table 3, you can see that the Acer C110 and the ViewSonic V1250s have unusually small batteries – this is usually done to achieve the minimum possible system weight, sacrificing battery life.  Realistic battery life on these products is 28/12 = 2.3 hours, which disqualifies them from consideration by many users.  The two 14.1" products (Acer C300 and Gateway M275) have larger batteries because (a) the larger screen draws more power, and (b) it's more acceptable for a product with a larger screen to weigh more, so a larger and heavier battery is acceptable.  The Electrovaya is a special case. It's the only Tablet PC that uses a "slab" lithium-polymer battery, with resulting battery life of over 6 hours.  The remaining six Tablet PCs are all in the same range (37 - 48 watt-hours), providing battery life in the 3-to-4 hour range.

In order to reduce power consumption, almost all Tablet PCs use the "integrated" video controller that's built into the Intel 855 chipset.  The result is relatively low graphics performance.  Trying to run a typical 3D game on most Tablet PCs can be an exercise in frustration.  There are only two Tablet PCs that use a reasonably powerful "discrete" video controller -- the HP TC1100 and the Toshiba M200.  Both of these use an NVIDIA video controller, which provides decent 3D game performance.  Beware of Tablet PCs that use a discrete video controller from SMI (Silicon Motion, Inc.); SMI controllers don’t provide significantly better performance than integrated controllers.

Every Tablet PC vendor offers integrated wireless LAN (WiFi); the only variable is whether you want 802.11 "a", "b", "g" or some combination.  Not all vendors offer all combinations, so if you want a specific combination this will limit your choices of Tablet PC. 

Don't put too much value on the Intel "Centrino" brand.  In order for an OEM to use the Centrino brand, they must use three components: the Pentium M, the Intel 855 chipset, and an Intel wireless mini-PCI card. Since every Tablet PC in Table 1 use the Pentium M and the Intel chipset (except the Averatec, which uses an AMD processor), all the Centrino brand differentiation means in reality is that the product uses an Intel wireless card.  Since Intel tends to run behind the rest of the industry in offering new wireless cards, some vendors offer their Tablet PCs in both a Centrino version and a non-Centrino version. The Centrino versions are available with only a "b" or "b/g" card, and the non-Centrino versions are available with a dual "a/b" or triple "a/b/g" card, neither of which Intel has available yet, or with another vendor’s "b" or "b/g" card.

A few Tablet PCs offer integrated Bluetooth; so far this has not proven to be very important.

The weight of a Tablet PC is only important if you have to work on your feet while holding the system on your arm for long periods of time.  Otherwise, the weight of all the accessories and other gear that you carry in your briefcase or computer bag generally is much more significant than the one- or two-pound difference between models of Tablet PC.  The weights of all the Tablet PCs in Table 1 are shown in Table 4, in order of increasing weight.

Table 4: Tablet PC weights in pounds

Most of the OEMs’ weight specifications should be taken with a large grain of salt.  For example, the M1400’s online specification sheet lists the weight as "approximately 3 lbs.".  As shown in Table 4, the actual weight of the M1400 is 3.4 pounds with the standard 40 watt-hour battery.  The M1400’s downloadable specification sheet lists the weight as "3 lbs." and includes the following footnote in very small type: "Weight represents approximate system weight with a 3-cell 20 WHr battery, empty PCMCIA slot, and no pen". (It’s difficult to use a slate Tablet PC without a pen!) The half-populated (20 WHr) battery pack is offered as an option mainly to reduce the datasheet weight. Very few people buy a half-populated battery pack, since it cuts the battery life by more than half. Note also the absence of a decimal point in "3 lbs." – technically that allows the OEM to round down any weight between 3.49 and 3.00 pounds to "3 pounds". 

None of the Tablet PC weight figures include the pen, PC cards, attachable or external keyboards, slipcases, external optical drives, AC adapters, spare batteries, spare pens, modem cables, LAN cables or anything else that you're likely to carry with you.  For example, the Motion M1400's 3.4-pound weight rises to 4.6 pounds once the combination attachable keyboard/screen cover is included -- and this is an accessory that many users won’t want to be without.  Similarly, the HP TC1100's 3.1 pound weight rises to 4.0 pounds when the attachable keyboard is included. The bottom line is that the published weight figures mean very little. Caveat emptor!

Not surprisingly, the two 14.1" Tablet PCs in Table 4 are the heaviest at 5.7 and 6.2 pounds.  The seven 12.1" Tablet PCs range from 3.4 to 5.5 pounds, while the remaining two 10.4" Tablet PCs are the lightest at 3.1 and 3.3 pounds.  These numbers are quite logical -- products with larger screens weigh more.  The product diverging the most from the averages is the Averatec C3500.  At 5.5 pounds, it's on the high end of weight for a 12.1" product.  One reason for this is its internal optical drive.  In addition to adding its own weight, the optical drive causes the entire system to be thicker -- which increases the housing weight.

Beware of sub-standard key spacing (standard is 19 mm or 0.75").  Many of the 10.4" and 12.1" Tablet PCs in Table 1 have key spacing of 92% or 95%; the Fujitsu T3000 and Toshiba M200 are exceptions at 100%.  If you're a fast touch-typist, substandard key spacing can be a serious impediment to comfortable usage.  Key stroke also varies considerably; while standard is 3 mm, Tablet PC key strokes can be as small as 1.7 mm (57%).  Often these specifications are not listed on Tablet PC data sheets; if they are particularly important to you, it may be necessary to contact the vendor to obtain this information. If you have access to a Tablet PC you’re considering, place a ruler on the keyboard and measure the space occupied by 10 keys. Divide the result by 7.5 and multiply by 100 to calculate the percentage reduction.

OEMs who concentrate on vertical markets generally offer a wide variety of peripherals and accessories. The clear winner is Fujitsu, with a total of 38 peripherals and accessories. This includes 8 cases/straps/screen protectors, 4 docks/stands, 10 input devices, 7 cards/memory modules, 6 power options and 3 storage options. If your application requires specialized peripherals and accessories such as a medical-grade AC adapter, a charge-only cradle or an optional high-capacity battery, study the OEMs’ accessory lists carefully before making your selection.

Memory: The recommended memory size for a Tablet PC today is 512 MB.  Less than that hurts performance; more than that isn't necessary unless you're manipulating large Photoshop images or doing other highly memory-intensive activities.  The maximum memory specification of the Tablet PC therefore doesn't matter very much; it's one of those "spec competition" factors that don’t mean much to the buyer.

Hard Drive: Hard drives in the Tablet PCs in Table 1 are available from 20 GB to 80 GB. The size you should select depends on (a) the particular sizes offered by the OEM, (b) how much storage space you need, and (c) your budget.  If the vendor offers it, a hard drive with a higher rotational speed (7200 or 5400 rpm vs. 4200 rpm) will provide a small performance advantage.  Shock-mounted hard drives, such as the one in the Fujitsu ST5000, will usually have lower failure rates.

Expansion Slots: All the Tablet PCs in Table 1 include one or two PC card slots.  Some Tablet PCs include a Compact flash (CF) card slot; this isn't particularly significant because you can always use a CF card adapter in a PC card slot.  A few Tablet PCs include an SD/SM/MS/MMC card slot. While a 4-in-1 PC card adapter is available to handle all of these card formats, if you need this slot and a PC card slot in your application, then your choice of Tablet PCs is narrowed.

Ports: All the Tablet PCs in Table 1 include USB 2.0; the only variable is the number of ports (more is better).  Some Tablet PCs also include a Firewire (IEEE 1394) port; if you need this port for your application, then your choice of Tablet PCs is narrowed.  Every Tablet PC includes an external monitor connector and a wired LAN connector; most of the latter are 10/100 except for the Acer C300, which is 10/100/1000.  Most Tablet PCs include IrDA, although very few commercial users actually use it.  A few Tablet PCs include a wireless (infrared) keyboard port, which allows eliminating the external keyboard cable.

Audio: Most of the Tablet PC in Table 1 have very similar audio systems.  The exception is the Motion Computing M1400, which has two internal microphones (a "microphone array") that can record audio omnidirectionally (e.g., everybody in the room) or unidirectionally (e.g., your own voice while suppressing background noise).  In most Tablet PCs in Table 1, the single internal microphone is unsuitable for any use -- a headset with a "close talk" microphone is required for serious audio applications such as speech recognition. If you have a choice, select a USB headset over an analog headset.

Digitizer: All the Tablet PCs in Table 1 use Wacom's batteryless pen, except the Averatec which uses a Sunrex digitizer with an AAAA battery in the pen.  Performance of the digitizer (accuracy, jitter, linearity, etc.) varies somewhat between Tablet PCs due to different integration details by the OEMs.  This is a constantly changing characteristic as OEMs tweak minor aspects of their products during production, so digitizer performance isn't really a valid selection criteria.

Security: A few of the Tablet PCs in Table 1 include a fingerprint sensor, which is both a useful security device and a terrific convenience enhancement.  You can use the fingerprint sensor to completely replace all logon names and passwords for every web site you regularly visit -- once you've tried it, you'll never want to be without it!

Docking connector: Many of the Tablet PCs in Table 1 include a docking connector (sometimes called a "system interface connector").  A docking connector is useful because it allows the Tablet PC to be placed in a desktop docking station.  Such stations typically include an optical drive, additional USB ports, a power input connector and other useful I/O connectors.  A Tablet PC with a docking connector can also make use of a port replicator, which allows quick connection/disconnection to the rat’s nest of cables under your desk.  If this functionality is useful to you, be sure to check the specs for the presence of a docking connector.

Modem: All the Tablet PCs in Table 1 include an internal wireline modem.  The difference between V.90 and V.92 is not significant in most applications.

Environmental Specifications: All of the Tablet PCs in Table 1 have similar environmental specifications -- for example, 5-35°C (41-95°F) operating temperature range.  Commercial Tablet PCs simply aren’t designed for use outdoors in locations such as Minneapolis, Minnesota in winter or Phoenix, Arizona in summer.

Selecting a Tablet PC is no different than selecting any other computing device.  There is no "best all-around product" -- it depends on your application and your particular needs.  Each Tablet PC has its own strengths and weaknesses; Table 5 lists some of the superlatives. It's important to analyze and understand each of the 23 factors described in this article before making your selection.

Table 5: Superlatives of Tablet PCs considered in this article