Released in 1989, it was received with excitement from most critics but with very poor sales to consumers. Seemingly no expense was spared in the construction of the machine. It featured a black and white active-matrix LCD screen in a hinged cover that covered the keyboard when the machine was not in use. The mouse 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 architecturally similar to a fast Macintosh SE, using the 68HC000, a low-power version of the Motorola 68000, running at 16 megahertz on a 16MHz bus. The Portable came with 1 MiB of RAM soldered on the motherboard and was expandable to 5 MiB using the single RAM expansion slot, or 9 MiB using the single PDS expansion slot (which due to strict FCC regulations was not developed for use with any other expansion cards, like the popular Ethernet card for the SE). It also had a single ROM expansion slot which would accommodate up to 4MB, though the Portable itself used a 256K ROM based on the SE's. Weighing in at 15.8 pounds (7.2 kilograms), due in large part to the sealed lead-acid batteries used, the machine was widely considered more of a "luggable" than a portable, which compared to the PowerBook series introduced a few years later, lacked the ergonomic layout that set the trend for all future laptops. On the plus side, it had a full travel keyboard, and battery life was up to 12 hours. The Mac Portable had a standard 1.44 MB floppy disk drive, an optional internal hard disk (a low-power 3.5" drive from Conner was used) or second internal floppy drive, and also offered the first optional internal modem in a Macintosh. In addition it also offered a full complement of standard-sized desktop peripheral ports (though the use of the internal modem disabled the external modem port). It even included stereo audio output, the only one included on a 68000 Mac. The modular, 'snap together' physical design of the Portable made it easy to upgrade, customize and repair in the field. Memory, modem and special-purpose circuit boards could be inserted in seconds without special tools, simply by opening the large panel that covered the back of the computer. Users could even move the trackball from the right to the left of the keyboard to accommodate left-handed users, or replace it with the optional numeric keypad. In addition, the Portable included many forward thinking features which were rarely implemented, if ever taken advantage of. The Portable was capable of SCSI Disk Mode, first officially supported by Apple with the PowerBook 100, through a third party kit and allowing it to be used as an external drive for a desktop Mac. It was also the first Mac with a self-contained display to include a built-in monitor output, requiring an external Video Adapter which Apple canceled shortly after it was announced, something even the PowerBook line would not incorporate until its second generation models. However, third party developers did create products, which included an overhead projector panel. It was also the first Mac to allow its display settings to be completely controlled by software, a feature that would later turn up in the Macintosh Classic desktop. Perhaps the most prominent feature of the Portable and the single item that contributed most significantly to its cost was the much praised active matrix LCD, which had a bright, sharp display comparable to a desktop Mac. Apple's use of the more expensive technology made it a standout from the PC portables which used an inferior and cheaper passive-matrix display.
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 white power supply had a very low output. This is also why in many instances the hard drive would not spin up. One workaround is to use the power supply from the PowerBook 165c/180c, which has a 3.0A output. (M5652). A DataGeneral power supply model 10094 which was used for model 2200 computers can also be substituted for the Apple dongle. It has a 6.4v DC output at 3.0A. Cut off their connector and attach alligator clips to the internal battery contacts. A hard wired plug could also be used, though alligator clips don't require soldering. As these batteries are all over 15 years old, it is very rare to find an original battery that will hold charge, and therefore allow the computer to start. It is possible to repack the battery with new cells, or use alternative 6 V batteries. The sealed lead acid cells used in the Portable's battery pack were made by Gates and were also used in Quantum 1 battery packs for photographic flash use. Sealed lead acid cells do not take well to being fully discharged.
One of the drawbacks of the Portable was poor readability in low light situations. So in February 1991, Apple introduced a backlit Macintosh Portable (model M5126). Along with the new screen, Apple changed the SRAM memory to pseudo-SRAM (which reduced the total RAM expansion to 8MB) and lowered the price. The backlight feature was a welcomed improvement, but it came with a sacrifice: battery life was cut in 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.
Despite the machine's disappointing sales, it was a brave attempt at making a workable portable computer, at a time when it didn't seem obvious what form such a personal computer should take. The Portable was limited by the available battery technology of the day, including its heavy and large Lead-acid batteries, but it was a revolution for mobile workers in Mac-based environments. Prior to the Portable, the only 'mobile' options for Mac users were small desktop Macs (like the Mac SE) carried from location to location in large padded shoulder bags, or third-party computers like the Outbound Laptop, a Mac-compatible that, for copyright reasons, required the user to supply Mac ROMs (which usually meant having to buy a new or used Macintosh such as a Macintosh Plus as well, making it far more expensive than an equivalent Windows laptop).
The first truly portable Macintosh was the PowerBook, but the Mac Portable was a significant step on the way, even if only to show what form such a machine shouldn't have. The Portable did not disappear completely with the release of the PowerBooks, however: the PowerBook 100 is in fact a Mac Portable compressed into a small enclosure. Apple sent the Portable plans to Sony, who miniaturized the components and manufactured it for Apple. It retains almost all of the features of the Portable with the notable exception that it lacks the popular, but expensive, active-matrix screen. It also eliminated the rarely utilized external video port as well as the internal PDS expansion slot and internal floppy disk drive. It sold for less than a third the cost of the Portable. In many respects the 100 is what the Portable should have been.