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The Macintosh Portable was Apple Inc.'s first battery-powered portable Macintosh personal computer. Released on September 20, 1989, it was received with excitement from most critics but consumer sales were quite low. It featured a fast, sharp, and expensive black and white active matrix LCD screen in a hinged design that covered the keyboard when the machine was not in use. The Portable was one of the early consumer laptops to employ an active matrix panel, and only the most expensive of the initial Powerbook line, the Powerbook 170, used one, due to the high cost. The cursor pointing function was handled by a built-in trackball that could be removed and located on either side of the keyboard. It used expensive SRAM in an effort to maximize battery life and to provide an "instant on" low power sleep mode. The machine was designed to be high-performance, at the cost of price and weight. ==Criticism== Unlike later portable computers from Apple and other manufacturers, the battery is charged in series with the supply of power to the computer. If the battery can no longer hold a charge, then the computer cannot run on AC power and hence it will not boot. The main reason for this is that the original power supply had a very low output. This is also why in many instances the special low-power hard drive would not spin up. Several popular unauthorized workarounds were devised, including to use the power supply from the PowerBook 100 Series which provides a higher output. As with automotive batteries, the sealed lead acid cells used in the Portable failed if they are fully discharged. The batteries are no longer manufactured and it is very rare to find an original battery that will hold charge and allow the computer to start. It is possible to repack the battery with new cells, or use alternative 6 V batteries.〔 ("Alternate Battery for Mac Portable" ). Low End Mac. Retrieved January 8, 2013.〕 There were three lead-acid cells inside the battery; each were manufactured by Gates Energy Products (now EnerSys) and they were also used in Quantum 1 battery packs for photographic flash use. Despite the dramatic improvement in terms of ergonomics offered by the responsiveness, sharpness, and uniformity of its active matrix panel, one of the drawbacks of the Portable was poor readability in low light situations. Consequently, in February 1991, Apple introduced a backlit Macintosh Portable (model M5126). Along with the new screen, Apple changed the SRAM memory to less expensive and more power-hungry pseudo-SRAM (which reduced the total RAM expansion to 8 MB) and lowered the price. The backlight feature was a welcomed improvement, but unfortunately it reduced the battery life by about half. An upgrade kit was also offered for the earlier model as well, which plugged into the ROM expansion slot. The Portable was discontinued in October of the same year. In addition, at 16 pounds (7.2 kilograms) and 4 inches (10 centimetres) thick, the Portable was a heavy and bulky portable computer. The main contributor to the weight and bulk of the Portable was the lead-acid batteries. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Macintosh Portable」の詳細全文を読む スポンサード リンク
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