Leading Edge Model D

The Leading Edge Model D was an IBM clone computer first released by Leading Edge Hardware in July 1985. It was initially priced at $1,495 configured with dual 5.25" floppy drives, 256 KB of RAM, and a monochrome monitor. It was manufactured by South Korean conglomerate Daewoo and distributed by Canton, Massachusetts-based Leading Edge. Engineer Stephen Kahng spent about four months designing the Model D at a cost of $200,000. Kahng later became CEO of Macintosh clone maker Power Computing.

In August 1986, Leading Edge cut the price of the base model by $200, to $1,295, and increased the base memory of the machine to 512 KB.

The Model D was an immediate success, selling 100,000 units in its first year of production. It continued to sell well for several years, until a dispute with its dealers forced Leading Edge into bankruptcy in 1989.

The Model D initially featured an Intel 8088 microprocessor at 4.77 MHz, although later models had a switch in the back to run at 4.77 MHz (normal) or 7.16 MHz (high). Earlier models had no turbo switch and ran only at 4.77 MHz, while a few of the later ones (seemingly very rare) were 7.16 MHz only. Three models are known: DC-2011, DC-2010E, and DC-2011E. The "E" seems to correlate with the capability of running at 7.16 MHz.

Unlike the IBM PC and IBM PC/XT, the Model D integrated video, the disk controller, a battery backed clock, serial and parallel ports directly onto the motherboard rather than putting them on plug-in cards. This allowed the Model D to be half the size of IBM's models. There were four full-length ISA expansion slots available.

The motherboard came in eight different revisions: Revision 1, 5, 7, 8, CC1, CC2, WC1, and WC2. A list of motherboard part numbers and revision numbers can be found here. Revisions 1 through 7 were usually found in model DC-2011, with revisions 8 through WC2 being either in 2010E or 2011E. WC1 (presumably also WC2) is 7.16 MHz only. Due to its tight integration, the Model D motherboard was a nonstandard form factor, so replacing the motherboard with an off-the-shelf upgrade was not possible.

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