If you don’t own a tablet, find an inexpensive one and give it a try. You may need a little time, but it won’t be too long before you appreciate its portability and power. I became a tablet convert after buying the Google Nexus 7 (Fig. 1). Apple’s iPad is a great platform, but it’s a bit large and expensive for my tastes (Fig. 2).
The iPad wasn’t the first tablet on the market, but it revealed the platform’s broad potential with consumers. Previously, tablets had only proven valuable in niche markets. Now, the iPad has a lot of competition, and innovation is rampant.
Tablets Large And Small
It seems like there are too many tablets to even consider (see the table). The benchmark, though, is Apple’s latest iPad with its large Retina display. Smaller tablets got a boost from Google’s Nexus 7, which provided a cheaper, more compact platform. It included Android 4.1, the latest version of Google’s Ice Cream Sandwich.
Barnes & Noble and Amazon have updated their 7-in. models with higher-performance solutions: the Nook HD and HD+ (Fig. 3) and the Fire HD (Fig. 4), respectively. But unlike Google, these companies aren’t targeting the larger space dominated by the iPad. Apple may have its eye on this arena and its attractive $199 price point with the rumored iPad mini, but the competition already is fierce.
Dell’s Latitude 10 is one of the many tablets designed to run Microsoft’s Windows 8 on Intel’s new Z2760 Atom, codenamed Clover Trail (Fig. 5). These platforms can run PC Windows apps, which is an advantage. For now, they will cost more, but they’ll also have more memory. They target the coprorate market, where Windows dominates the PC space.
Another new group of tablets uses MIPS-based platforms running Android. They’re just starting to show up, mostly on the international market, such as the Philips T7 Plus (Fig. 6), which is based on Ingenic’s dual-core JZ4780 (Fig. 7).
In many ways, the tablet market reflects the PC’s heyday. But differentiation is harder because of the similarities in physical appearance. You may be able to spot the differences between two tablets when they’re side by side. But they’re still essentially a rectangular LCD with a touchscreen.
Tablets typically have three buttons, including power and two volume controls. There may be holes for microphones and speakers, as well as a tiny lens for a camera. You’ll find at least one connector on the edge, usually USB. But sometimes, it’s disguised as a special connector for “advantages” that may be real or imagined.
At least with PCs, the monitors were different and the cases were varied. Even laptops have some level of expansion. Tablets tend to be more like smart phones. They’re very fixed, with expansion limited to micro-SD storage. So the real difference is under the hood, where the electronics and software reside.
Tablets, Software, And Stores
When the tablet and smart-phone market began to take off, there was speculation that operating systems would disappear and applications would dominate. That hasn’t actually happened, but apps and app distribution have become very important. Meanwhile, three operating systems rule the field-Apple’s iOS, Google’s Android, and Microsoft’s Windows. Others have found a niche or died a slow death.
Apple’s iOS provides compatibilty between its smart phones and tablets. Android takes the same approach, but each Android smart phone and tablet is responsible for delivering and updating its operating system, leading to a wider level of compatibility concerns between systems.
Windows is an interesting case. Windows on a smart phone isn’t the same as Windows on a PC, but the operating systems all carry the Microsoft and Windows names. Microsoft also has a version of Windows for smart phones with ancestry that started with Windows CE, which targeted the Arm platform among other non-x86 targets.
Windows on tablets doesn’t come from these roots. Instead, it’s drawn from the PC side, which is why Intel’s system-on-chip (SoC) is so important in the tablet space. It allows the latest Windows 8 x86 code to run on these new tablets.
Just to add to the overall confusion, a version of Windows 8 called Windows RT is designed to run on an Arm platform. It was designed from the ground up in conjunction with the x86 Windows 8 so they’re effectively the same code base, one that’s different from the Windows smart-phone track. The challenge for Windows RT is that it effectively competes with Windows 8 for tablets as well as iOS and Android.
Microsoft covers all the bases, but with an extremely varied set of solutions. Apple covers smart phones and tablets with one operating system. Android covers smart phones, tablets, and just about any other embedded device you can think of, from robots to coffee makers. Arm is the dominant processor architecture used with tablets, but Android runs on all major processor architectures including MIPS, Power, and x86. If the target can run Linux, which Android is based on, then it’s a candidate for Android.
Google unified Android with version 4 combining version 2 for phones and version 3 for tablets. There are still lots of older versions in use, though, leading to a very fractured collection of versions with core commonality.
Programming support for such a wide range of operating-system platforms is due to the move of many applications to programming frameworks based on just-in-time (JIT) compilation including Java and C#. Windows has this type of support from C# and other languages, but native code applications will likely be the pull for users of Windows 8 tablets. Still, the approach provides portability between Windows 8 and Windows RT.
This compatibility between platforms and the high level of connectivity of these devices has made the app store attractive to developers. Part of the “operating system” from a user’s perspective these days is the Web browser and the app store where applications can be downloaded directly to the device.
App stores are opportunities for developers because distribution of their products and services is easier. But it’s a double-edged sword. App stores tend to be mated to the operating system, forming a walled garden.
Apple’s app store is more like a walled fortress given the limitations on the hardware platforms. Google’s and Microsoft’s app stores are open to a wider set of hardware vendors. Android is one area where we see app stores focused on a single vendor’s products, including the offerings from Amazon and Barnes & Noble.
This does have major implications for the kinds and variety of applications available to users as well as how they will be supported by third parties. For example, set-top box remote control applications are available for many platforms enabled with Wi-Fi. Users then can see a list of programs and select the one to be viewed on their HDTV. Such an application might be found on Google Play, which is Google’s app store, but are unavailable for Barnes & Noble tablet owners.
Most of these software environments allow side loading, or the installation of apps that don’t come from the matching app store, but few users are versed in the option or methodology. Many vendors actively discourage or prevent this option from being employed.
Processors Target Tablets And Smart phones
Components drive much of the innovation in today’s tablets. In the future, the minimum platform will be sufficient for most users. Today’s tablet SoCs include a multicore CPU, a multicore GPU, and a host of additional interfaces and hardware acceleration blocks for multimedia support.
Arm takes center stage in the tablet market for its architectures, including variants of the Cortex-A series. The Cortex-A9 is the most common, showing up in the quad-core Nvidia Tegra 3 as well as Texas Instruments’ OMAP7740 and OMAP7750. The compatibility among Cortex-A9 platforms is high, although each SoC has its own peripheral set and possible “enhancements” that are handled via the operating system.
This state of affairs should make things simple, but it doesn’t. Some companies like Marell and Apple have an Arm architecture license or two for creating architectures that are different. Apple uses its A5 on the iPad and the A6 on the new iPhone 5 (see “Apple Rolls Its Own Dual Core A6 For The iPhone 5”). The A5 is akin to a Cortex-A9, but the A6 is more like a souped-up Cortex-A9 or a refined Cortex-A15.
Arm’s big.LITTLE architecture is likely to have an impact in the future as SoCs based on big.LITTLE show up (see “Little Core Shares Big Core Architecture”). The little and low-power side of the equation is a Cortex-A7. The big side is a Cortex-A15. A platform would typically consist of a single Cortex-A7 core and possibly multiple Cortex-A15 cores. The system would run one set or the other depending upon its requirements with an eye toward reducing power consumption.
All the Arm platforms in use are 32-bit cores with the 64-bit architecture on the horizon (see “ARM Joins The 64-Bit Club”). Initially, the 64-bit core will target the server space.
MIPS has 32-bit and 64-bit architectures, but the SoCs for the tablet market use the 32-bit variants. MIPS licenses its design like Arm, and MIPS is used in a wide range of products including those in the embedded consumer space. The MIPS architecture is known for high efficiency and low power, which are important in tablets.
The Z2760 Atom builds on Intel’s existing x86 architecture. It uses Intel’s 32-nm high-k metal gate process. The dual-core chip supports hyperthreading so it can run four threads simultaneously. This isn’t the same as four distinct cores, but it is much better than two cores.
Intel has built Atom SoCs before, but the Z2760 targets tablets, more specifically tablets running Windows 8. It can run any 32- or 64-bit x86 operating system including Linux/Android, but don’t look for any Z2760 Android tablets anytime soon. Intel and its partners are putting its Z2760 support behind Windows 8.
Intel also has spent a lot of time on the design of the power management. Two new power management states, S0i1 and S0i3, reflect the ways a tablet will be used. S0i1 is designed for an idle system that is not yet in sleep mode. S0i3 is a sleep mode used when the device is connected via a wireless link. It can flip to full-speed mode in milliseconds while consuming microwatts.
Comparing architectures and performance with other platforms like Arm or Intel is always a challenge. Numbers of cores and gigahertz aren’t good for comparison even within the same architectures. A single-core Cortex-A15 will run rings around a Cortex-A9 running at the same clock rate.
Comparisons on the GPU side are even more difficult because the architectures are unique. In general, HD playback speed is more important, and most hardware easily handles it. Power consumption is more important.
Gaming also takes advantage of the graphics hardware, and this is where the GPUs can shine. GPUs also can be used to offer compute support using frameworks like OpenCL. Not all GPUs will provide this kind of support.
Virtualization is one CPU feature that may become more important in the future. It may come into play from a vendor or enterprise perspective where virtual machines would be used for security or digital rights management support.
Security needs to start at boot time. Secure boot isn’t really being discussed with respect to most tablets yet, and it’s not found on most tablets. But it will be important in the future, especially for enterprise use.
The display is a tablet’s most visible feature. Apple’s Retina display pushes pixel size to the limits of human eyesight. Feature lists of tablets, and also smart phones, now include PPI (pixels per inch) information. Side-by-side comparisons can highlight differences between devices, but these days most platforms will approach Retina’s resolution.
PPI is only a good comparison when discussing the same type of viewing environment. For example, a PPI for a smart phone viewed at a typical distance of 10.5 in. needs to be higher than a tablet that will normally be viewed at 13 in. or more. HDTVs running at 1080p are essentially “Retina displays” when viewed from the proper distance. Resolution isn’t the only important spec in displays, though. GPUs typically dictate the frame rate that can be delivered. Color and display quality are important as well.
The DisplayMate visual test tool can be used to benchmark the brightness, contrast ratio, color gamut, and other specs of all types of displays. In fact, Raymond Soneira, president of DisplayMate Technologies, recently compared the Kindle Fire HD, Apple iPad, and Google Nexus 7.1
“I was surprised at how well the Kindle Fire HD display performed, first that it handily beat the iPad 2 and then that it came close in performance to the new iPad display, which has the highest picture quality and accuracy of any consumer display we have ever tested,” he said. “On the flip side I was surprised at the display firmware bugs and poor calibration of the Nexus 7 and the resulting poor picture quality. Hopefully Google will correct them with a software and firmware update.”
Most tablets offer multitouch and capacitive touch these days. Resistive touch has been a less expensive (though a less responsive) option, but low-cost capacitive touch has effectively eliminated its competitor from tablets. Resistive touch and other touch technologies remain important in other application areas.
The touch interfaces probably have more impact on cost, size, and operation than any other item within a tablet design. Touch interfaces initially required thicker displays with multiple layers. The trend is toward minimal layers and direct lamination to the LCD screen, resulting in thinner tablets and smart phones. Fewer and thinner layers also make a difference by improving display brightness while keeping or reducing backlight power requirements.
Most tablets support at least two-touch input to allow pinch-zoom gestures, but that’s the minimum. One of the latest specs showing up is the 10-touch feature, enabling the system to detect the position of 10 fingers on the screen. It’s great for fingerpainting and makes typing on a screen-based keyboard more accurate.
Often, the ability to detect large objects touching the screen like a palm or thumb isn’t discussed unless it’s available. Tablets that have smaller border bezels are more likely to offer this feature, which will become more important as borderless tablets become available. Borderless displays are already possible using technologies like Cypress Semiconductor’s SLIM (single layer independent multitouch) technology (see “Single Layer Multitouch Cuts Cost In Half”).
Flash memory is the nonvolatile memory of choice for virtually all tablets. It tends to show up in fixed amounts of 8, 16, 32, and 64 Gbytes. Expansion is possible on some tablets with SD or micro SD sockets, which are very handy for tablets with minimal on-board flash memory.
The alternative is online storage. Most tablets acquire apps and stream multimedia content wirelessly, so it makes sense to utilize connected storage. Internet-based storage includes Apple’s iCloud, Google’s Drive, and Dropbox. Local file servers accessed via wireless local-area networks (WLANs) are another option.
Seagate’s GoFlex Satellite is one alternative for personal storage that can be used anywhere (Fig. 8). It looks like a USB hard drive, which it is, but it has its own battery and Wi-Fi interface since it’s essentially a mobile file server. Download an app for iOS or Android, and a tablet can then access the GoFlex Satellite. It can stream HD video and other multimedia information in addition to providing document and application storage.
Some apps can utilize the GoFlex Satellite directly, while others will require movement of information to or from the tablet using other means. This isn’t unusual. In fact, it’s the case for many Internet-based storage facilities available for tablets. Tablet storage like the GoFlex Satellite will be important to users who utilize large files like videos or those who generate content including documents that need to be stored locally.
Power usage is an issue for any wireless device, but video streamed from the Internet must go through the tablet’s Wi-Fi interface. Using a local device like the GoFlex Satellite does not require any more tablet power than the Internet connection.
Other Tablet Stuff
Audio is near the bottom of the feature list for most users. Built-in speakers range from fair to next to useless. External speakers, headphones, or wireless Bluetooth headsets tend to be required for more than casual use. This isn’t an issue in many cases since headphones provide privacy in environments like airplanes, living rooms, or offices.
The quality of the audio rendering also varies significantly on tablets, but here the range is from fair to excellent. Some tablets even provide audio enhancement such as surroundsound support like Dolby Digital.
Most tablets have internal batteries. Charging is typically via USB. Higher power delivery via USB is now possible (see “New USB Spec Improves Charging In Portable Devices”). The new standard can deliver up to 100 W compared to the 2.5 W that USB could originally provide. This means faster charging time for tablets and other mobile devices such as smart phones.
Dell’s Latitude 10 will have a removable battery. Removable batteries offer many advantages, but they tend to make the tablet thicker so there are tradeoffs.
Wireless charging is an option that has yet to penetrate the tablet market, but it does eliminate the need for the often only remaining connector (USB) on the tablet.
The horizon is bright for tablets, but many platforms and vendors will fall to the wayside as the competition continues to heat up. For now, the wide variety of choices in all aspects of tablet design makes this area ripe for innovation.
- “7 inch Tablet Display Technology Shoot-Out,” Raymond M. Soneira.