CPU power consumption has also improved steadily during the last decade with new chip processes, shrinking feature sizes, and lower voltage levels. Operating systems have also become more efficient, slowing or stopping processors to save power when full speed was not needed. Transmeta s voltage and clock rates can be changed on the fly, and their benchmarks show substantial power saving over x86 processors at comparable application speeds. The REB claims 20-40 hours between charges, depending upon settings and usage, and the SB claims 5 hours. These are respectable figures using today s technology, and we can look forward to improvement.
Storage is another key element.
This is sufficient for reading on a plane or a weekend vacation, but it is not the lifetime library Vannevar Bush dreamt of. Screen technology has not improved as quickly as electronics or storage. We have not seen Moore s Law improvements in pixel density, contrast, power consumption, and so forth, but costs are falling. The reading area on the REB screen is about 3 x 4.5 inches and the SB 5.9 x 7.5. On the other hand, it is fine for more limited reading, and the small screen saves power, allows a slower processor than the SB, and results in a smaller, lighter device.