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Notebooks Evolve into Affordable Desktops, Mobile Second PCs
Falling LCD panel prices have opened up a new market for desktops with LCD displays, while a reduction in power consumption of MPUs, LCDs and HDDs has boosted notebook mobility.
Notebook personal computers (PC) are at a major point in their evolution as they begin to branch into two directions to meet the requirements of two different groups of users: those who use notebooks primarily as desktop systems, and those who prefer to use their notebooks on the road. Until now, both groups have used the same machines.
Focusing on One Market
In the future, notebook PCs will move in user-specific directions to meet these different requirements. Models for desktop users will no longer be restricted by the notebook form factor and will become compact desktop PCs with liquid crystal displays (LCD) as standard. Notebooks for those on the move, on the other hand, will stress mobility above all: lightness, thinness, and length of battery drive time.
The trigger for this revolution is the sudden widespread adoption of LCD desktop machines. Users who might have purchased notebooks for their desktops are choosing low-priced LCD desktop models instead (Fig 1).
As a result, notebook PC manufacturers aiming at mobile applications can now concentrate their product planning efforts on mobile systems, and stop taking into account the people who use the same machines on their desks.
Lower LCD Prices
LCD desktop PCs have been around for some time. IBM Corp of the US, for example, released the PS/55E with a 10.4-inch thin-film transistor (TFT) LCD in October 1993. Until recently, however, they were unable to capture much of a market.
The first signs of a change in the situation occurred at the end of 1997, when the prices of LCD desktop PCs dropped to the level of "best-selling" notebook PCs, kick-starting the market. The unit prices of LCD panels were dropping (Fig 2), resulting in a much smaller price difference between the 12.1- to 13.3-inch panels used in notebooks, and the 13.8-inch or larger panels used in desktop PC models.
If users who want a space-conscious PC can get a large-size display for the same price as a notebook, then there is no reason for them to choose a notebook design. According to a source at the Mobile Products Department of Sony Corp, the LCD desktop PC covers essentially the entire compact-PC market previously supplied by notebook PCs.
One large PC store in Akihabara, the largest electronics district in Tokyo, claims that more and more customers coming in search of a notebook, end up buying an LCD desktop machine instead. The same trend is evident among corporate users. "There are an increasing number of notebook users who choose an LCD desktop model instead of replacing their old notebook with a new one," says Norimasa Sagawa, manager, Planning Department, Personal C&C Customer Communications Division at NEC Corp of Japan.
Mobile as Second PC
Models designed specifically for mobile computing will be totally different from existing notebook PCs or the LCD PCs aimed at desktop use. This is because the mobile machine user is assumed to already own a desktop PC or an existing notebook (Fig 3).
Users who are looking for a second or third machine to augment their primary machine, want unique features quite different from their workhorse.
This same trend applies to users buying mobile notebooks. Instead of demanding function and performance on a level with desktop systems, the emphasis is on the mobility that notebooks provide best. As an example, some 80% of the Mobio B5-sized notebooks, released in the fall of 1997 by NEC, were sold as second or third machines.
New Power-Saving Technology
New technologies enhancing mobility include Li-polymer rechargeable batteries, reflective LCD panels, and embedded reduced instruction set computer (RISC) microprocessors. Li-polymer rechargeable batteries contribute to thinner PC cases; reflective LCD panels enable thinner design and reduced power consumption; and embedded RISC microprocessors contribute to lower power requirements.
A combination of reflective LCD panels and Li-polymer rechargeable batteries, for example, could be used to make a model only 12.7mm thick. If a RISC microprocessor is combined with the reflective LCD, the resulting system could enjoy a battery drive time of over 30 hours.
"The biggest power hogs in notebook PCs have been the microprocessor, the LCD panel and the hard disk drive (HDD)," explains Kuniaki Saito, project manager, Engineering Department I, Mobile Computing Division, Fujitsu Ltd of Japan. "Together, they accounted for 60 or 70% of the total power consumption." In a B5-sized notebook consuming about 12W, for example, the microprocessor uses 2 to 4W, the LCD panel 3W, and the HDD 1 to 2W. Improved mobility demands a reduction in power consumption.
New technologies that reduce power consumption have recently entered practical use (Fig 4). One technology is a result of WindowsCE, the new embedded-application operating system (OS) developed by Microsoft Corp of the US. Because of the new OS, it has become easier to develop models using RISC microprocessors, and RISC chips enjoy lower dissipation only several hundred mW, around 5% of the power gobbled up by an 86-family microprocessor from Intel Corp of the US.
Another important technology is the reflective TFT-LCD panel; because no backlight is needed, it uses only 1/5 to 1/7 the power of a conventional color TFT-LCD panel.
Thin (under 5mm) Li-polymer rechargeable batteries are also practical now. They don't contribute to reduced notebook power consumption, but make thinner designs possible.
Adoption of these technologies significantly improves notebook PC mobility. Assuming they were all implemented in a B5-sized notebook, the overall power consumption would be reduced to between 0.7 and 1.7W. Weighing under 600g and half an inch (12.7mm) or less thick, this machine would have a battery drive time of 24 hours (Table 1).
There are problems, however, preventing immediate adoption of these new technologies.
If a RISC microprocessor is adopted, the application software will be different to desktop PC software. If the reflective color LCD panel is used, the notebook will not be able to be used in all environments it would be difficult to see the display in hotels, on airplanes, in coffee shops, or in other relatively dark environments. And since the volume production lines for Li-polymer rechargeable batteries have only just been established, prices remain high.
Notebook PC manufacturers must balance these problems against the potential gains in mobility.
Fans Needed for Over 5W
According to Yasuhiko Hosoya, manager, PC Products Development, Lios Systems Co, Ltd of Japan, "5W is best" for microprocessor dissipation in mobile computers. With dissipations of 5W or less, cooling can be handled with just a heat sink (Fig 5).
Over 5W, however, cooling fans generally become necessary. The thinnest cooling fans for notebook PCs are 6.6mm thick, which is out of the question for a product prioritizing thinness.
It appears that future generations of MPUs based on the x86 architecture will continue to exceed 5W. At a developers' conference in February 1998, Intel stated that microprocessor chip dissipation will continue to increase at a rate of about 1.35 times every 18 months (Fig 6).
The Pentium II processor shipped in April 1998 for notebooks, for example, has a dissipation of 6.8W at 233MHz, and 7.8W at 266MHz. "We recognize that the current Pentium II processors are not optimum for use in sub-notebooks," admits Akio Tomobe, senior application engineer, Mobile Platform at Intel Japan KK. The 333MHz chip scheduled to appear in the first half of 1999, code-named Mendocino, is expected to have a dissipation of 9.5W.
Controlling RISC Dissipation
As long as notebooks are restricted to 86-family chips, a steady increase in dissipation seems unavoidable, and this will lead more and more notebook PC manufacturers to offer designs using embedded RISC chips. The fact that the WindowsCE operating system makes it possible to provide desktop users with a familiar user interface is further accelerating this trend.
Compared to 86-family microprocessors, the embedded RISC microprocessor has extremely low dissipation. The Persona machine from Hitachi Ltd of Japan, with WindowsCE, uses the firm's SH-3 100MHz RISC chip, and offers a dissipation of only 0.2 to 0.3W. This is only about 5% of existing notebook designs with 86-family chip. This means that no special cooling mechanisms are required.
However, even in RISC chips, a gradual rise in dissipation seems certain, because higher frequencies and enhanced processing performance are demanded.
This means that innovations will be required to keep any dissipation increase to a minimum. Two main technological issues are involved in reducing power dissipation.
The first is to reduce the supply voltage. The key point here is circuit technology to minimize current leakage, because the lower the supply voltage, the harder it becomes to ignore transistor leakage current.
The second issue is integrating peripheral circuits into the microprocessor chip. Candidates would include dynamic random access memory (DRAM), and external interface control circuits such as those for IEEE1394.
Sharp Leads in Reflective LCDs
Reflective color LCD panels, which offer significantly lower power consumption because they do not require backlights, have entered the realm of the practical. "Within a year," predicts Tatsuhiko Ikuno, division general manager, Personal Computer Division, Sharp Corp of Japan, "notebook PCs with reflective panels will be commercialized."
The power consumption of a 6.5-inch reflective panel with 640- x 240pixel resolution, for example, is 0.2W (Table 2), considerably lower than the 1.4W consumed by a conventional color TFT-LCD panel with a backlight. Further, if a reflective panel is used, thickness and weight can also be reduced. A 6.5-inch panel is only 2.2mm thick, about a third of a backlit model, and weighs only about half, at 80g.
A number of LCD panel manufacturers are already marketing reflective panels. While they offer low power consumption they also suffer from poor image quality: displays are dark and the color purity is low. As a result, they are not being used in notebook PCs.
The reflective color TFT-LCD announced by Sharp in September 1997, however, was different (Fig 7). "There are still some problems with image quality, but it is more than usable. We are starting to test the LCD panel for adoption in notebook PCs," says a PC engineer.
Sharp appears to have established a solid lead over its competitors in reflective color LCDs. An engineer at a PC manufacturer commented, "We obtained samples of reflective panels from a number of firms, and Sharp was significantly better in image quality." Some notebook manufacturers, however, are worried about getting trapped in a single-source situation.
Low Visibility in Dark Places
There are, however, still two problems with reflective panels.
First, power consumption shoots up as the screen size increases. A 12.1-inch reflective panel with an 800- x 600-pixel resolution uses 0.4 to 0.5W, more than double that of a 6.5-inch panel. This is because of the higher drive circuit frequency, and the excess power that drives consume. The 640- x 240-pixel panel runs at 13MHz, while the 800- x 600-pixel panel runs at 40MHz. This can be controlled somewhat by drive circuit innovations and a reduction of panel parasitic capacitance.
Second, the displays are almost impossible to see in a dark environment. "We prototyped a machine running a reflective panel with WindowsCE, and tried it out in a variety of environments," said Shoji Narisawa, senior manager, 1st Product Department, Personal Workstation Division at NEC. "We couldn't read the screen in dark places like coffee shops and the product proposal was scrapped."
In response to this situation, Sharp developed a method of illuminating the display with light from the front (Fig 8), called "front lighting."
Three methods are proposed. The first is a point light source, where a light source like a lighthouse is positioned at one end of the panel, illuminating the entire panel. The source is a white light emitting diode (LED).
The second method is a line source, where a line of white LEDs are mounted along the top edge of the panel for illumination.
In the third method, a planar source is mounted on the top edge of the LCD panel. Sharp has not disclosed the third method in detail.
Li-Polymer Production Ready
Li-polymer rechargeable batteries will also contribute to thinner notebook PCs, and the new power sources are already available. Ultralife Batteries, Inc of the US, for example, has already begun volume production for the Pedion design from Mitsubishi Electric Corp of Japan. Competitors Hitachi Maxell, Ltd and Yuasa Acep Ltd, both of Japan are ramping up now, while major battery manufacturers like Sanyo Electric Co, Ltd and Sony Corp, both of Japan , say the technology is complete: "We are ready to begin volume production as soon as there's demand," they claim.
Li-polymer rechargeable batteries are thinner than Li-ion rechargeable batteries. Rectangular Li-ion rechargeable batteries add an additional 2mm to notebook PCs, meaning that the minimum total thickness would be about 7.2mm.
Li-polymer rechargeable batteries are targeting notebook PCs which demand battery pack thicknesses of under 7.2mm. As Yuasa Acep's representative director, Katsuji Ashida, points out, "We are using our thinness to approach notebook PCs which stress mobility."
Limited to New Models
It makes little sense for notebook PCs with high power consumption to switch to Li-polymer rechargeable batteries. Compared to the current Li-ion batteries, Li-polymer is more expensive and has a lower energy density (Fig 9). One engineer at a battery manufacturer estimates the unit price per energy capacity is about triple when compared to a cylindrical battery.
As the power consumption of the PC rises, the required capacity of the onboard batteries rises with it, increasing the overall price. The only way to reduce prices is to reduce the battery capacity, which means that system power consumption must be reduced.
As a result, Li-polymer rechargeable batteries are likely to appear in the new, thin notebook models which slash power consumption through the use of RISC microprocessors and reflective LCD panels.
by Hiroki Eda, Katsumi Yamashita and Yoichiro Hata
References:
- Fujitsu
- Hitachi
- Hitachi Maxell
- IBM
- Intel
- Microsoft
- Mitsubishi
- NEC
- Nomura Securities
- Rios Systems
- Sharp Corp
- Sony
- Ultralife Batteries
- Yuasa Acep
