PowerBook Duo 270c-series


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The PowerBook Duo 270c-series has a single motherboard memory expansion slot addressed along a 32-bit memory bus. These computers require unique 70ns Duo Memory Expansion Cards in either 4MB, 8MB, 12MB, 20MB or 36MB capacities. The Duo 200-series shipped in no fewer than six distinct configurations, with four different motherboard revisions:

• Logic Board, Duo 210, 25MHz 68030, part number 661-1653

• Logic Board, Duo 230/250, 33MHz 68030, part number 661-1672

• Logic Board, Duo 270c, 33MHz 68030 / 68882 coprocessor, part number 661-1717

• Logic Board, Duo 280/280c, 33MHz 68LC040, part number 661-0051

The Duo 270c configurations shipped with 4MB RAM soldered to the logic board. Although all Duo 200-series motherboard revisions accept the same RAM as the PowerBook Duo 2000-series, please note which PowerBook you are ordering for in the Comments field of the order form when ordering upgrade modules.

Including soldered main motherboard RAM, the addition of a single 4MB, 8MB, 12MB, 20MB or 36MB expansion module yields memory configurations of 8MB, 12MB, 16MB, 24MB and 40MB. Apple technical documentation (PowerBook Duo 250 and 270c: Differences (3/95)) suggests that 32MB is the maximum amount of RAM the Duo 270c can address, but satisfactory results up to 40MB have been attained through the installation of third-party 36MB expansion modules.

Alone among the Duo 200-series, the Duo 270c shipped with a Motorola 68882 floating point unit math coprocessor in addition to the standard 68030 microprocessor clocked at 33MHz. While the Duo 280/280c-series introduced the (then) fastest Mac PowerBook ever manufactured with a 33MHz 68LC040 microprocessor, the Duo 270c debuted the finest color LCD display ever deployed on a Mac laptop, and all color Duos have subsequently utilized the same display. It was not until the debut of the final PowerBook Duo, the Duo 2300, that the first PowerPC subnotebook came to market with a Motorola 603e microprocessor running at 100MHz. Despite high hopes among Duo aficionados, Duo 2300 performance benchmarks were disappointing, primarily due to sluggish video I/O and poor SCSI I/O rates.

The Duo-series in entirety support SCSI Disk Mode.