Breakthrough display

The XO's main selling point is its display. Only 7.5 inches across, the panel was developed completely anew by Chi Mei Optoelectronics (CMO) and is easy to read both in full sunlight and indoors, surpassing all common laptop displays in this respect. The panel has two modes of operation. Behind the layer of fluid crystals is a sort of sieve whose broad lattices reflect and refract ambient light. Because the color filters are behind it and therefore do not play any role in creating images, you see a black and white image in bright light (mode of operation 1). Thanks to an incredible resolution of 200 dpi (1200 x 900 pixels), text appears razor-sharp; other notebook displays have a long way to go to match this performance. The BTest-1 prototype has a reflecting display, while the BTest-2 machine does not.

With the XO's dual-mode display, the color image (righ) only appears with LED backlighting. Under ambient light, the bright latticework (left) reflects light, and the image appears in black-and-white.

Once the LED backlight is switched on, light passes through the color filters from behind and penetrates the holes in the distribution sieve, creating a color image (mode of operation 2). Each of the 1200 x 900 pixels is then either red, green, or blue. As it takes one green, one red, and one blue subpixel to create a pixel, the resolution of color images is only around 800 x 600. The DCON display controller provides for automatic antialiasing to smooth out edges. In addition, it refreshes the image even when the rest of the computer is on standby. Luminous intensity is only 64 cd/m2, half that of a normal notebook panel, and contrast leaves something to be desired at 82:1. But that's enough indoors, and outdoors the ambient light helps, though the more ambient light there is, the less color you see.

A few keys are provided to set the brightness of the display. The XO will also have a back light sensor, though the prototype either did not have one or it simply didn't work. In our measurements, we determined power consumption of 1.5 watts for the display, but power consumption is to be reduced down to one watt. This value may also be a new world record; other displays consume at least four times as much power.

Ergonomics and ports

A capacitive touchpad is found below the keyboard; you can move the cursor with your finger as usual. But in addition, the entire surface to the left and right of the touchpad can also be used for input because a resistive layer is below it. You can use a stylus to write on it or draw pictures.

Of course, the XO is designed to promote reading. The display can therefore be turned on its axis and closed on top of the keyboard as is done with the tablet PCs called "convertibles". But unlike them, the XO does not have a touch-sensitive display. A few keys and a navigation knob on the margin of the display, however, allow the Sugar user interface to be operated without one. Field tests currently underway may reveal whether the link connecting the convertible display to the keyboard will withstand handling by children. It might turn out to be a weak point. The organization has already sent some of the B2 prototypes to a few countries, including several hundred XOs intended for Brazilian schoolchildren. In addition, around 100 XOs have also been delivered to a test school in Galadima, Nigeria. No results have been published yet for these tests.

Ports are hidden to the left and right at the top of the display behind flaps. On the right, there are two USB ports; to the left, an audio port and an additional USB connection. The audio port also has a mode in which it serves as an input as an A/D converter, which is useful for handicraft projects using photo sensors or measurement devices, for example. The two flaps not only protect the ports, but also serve as WLAN antennas.

Battery or wind-up

A nickel metal hydride battery consisting of five cells stores 22.8 Wh, around a half to a third of what is normally found in notebooks. Lithium-ion batteries have been deemed too dangerous by the developers, but new lithium batteries may mean that the XO will eventually not contain NiMH, which discharge quickly.

Negroponte has a very optimistic target for the XO's power consumption: two watts. Compared to around 10 watts for even the thriftiest laptops, that would be an excellent performance, giving the machine of runtime of more than 10 hours despite the small battery capacity. The prototypes are nowhere near this performance because power management does not yet work. At present, the laptop runs for 2.5 hours with and 3.5 hours without display illumination, consuming 9.1 and 6.5 watts, respectively.

Low power consumption is important for areas without a connection to the grid or with only intermittent power supply. Power consumption has to be so low that the battery charge will cover most of the day and allow the small amount of power from a crank to charge it. Originally, the XO was designed with a crank inside the case. It turned out that the mechanical load was too great, so that this type of power supply has been taken off the drawing board. Now, a type of yo-yo is being discussed: the generator has a windup string and provides enough power for 10 minutes of XO operation from one minute of winding. The system has not, however, reached the prototype status yet.