Lower-capacity machines are user upgradeable to 640 KB. Motherboard revisions 7, 8, WC1 and WC2 come with 768 KB of RAM installed (640 KB available to the user). Some models have a monochrome/CGA selection switch, with a single port used for both modes. Some models have both a Monochrome and a CGA port, also with a switch to change modes (and ports). The Model D computers support a special extended graphics mode (EGA): 640x200. The buyer had the choice between a floppy disk model and a fixed disk (hard disk) model. The floppy disk model has one or two 360 KB drives, so that the user can run MS-DOS programs on the primary drive and work with files on the secondary drive, if equipped. The fixed disk model has one 360 KB floppy drive and either a 10 MB, 20 MB, or 30 MB hard disk. The model with the 20 MB fixed disk was initially released in February 1986 at a cost of $1,895. Leading Edge dealers had difficulty keeping the 20 MB model in stock. At the time, a Tandy 1200 equipped with a 10 MB drive sold for $1999. The buyer also had a choice between an amber or a green monochrome CRT monitor. Modern Upgrades Modern expansions are possible for the Model D, including the use of an XT-IDE 8-bit ISA card, which provides an Parallel ATA IDE port for hard disk drives and a compact flash card. Users wanting to use the XT-IDE in the Model D must set the address of the XT-IDE card within its BIOS to 340h, as not to conflict with the real-time clock address of 300h, which is the default address of the XT-IDE. However, it is possible to disable the Real-Time Clock by removing clip #2 from J13 and deleting the "DEVICE = CLKDVR.SYS" entry from the 'CONFIG.SYS'. The Model D also fully supports in the NEC V20 microprocessor in place of its Intel 8088 processor. This provides the Model D with expanded instruction sets and a 5-10% performance boost in normal operations. All Model D computers support the addition of an 8-bit or 8/16-bit VGA ISA card for VGA graphics. Software The unit comes with MS-DOS 2.11 or later, and a special edition of GW-BASIC to support the extended graphics mode. It also has a diagnostics disk. This disk contained a diagnostics program, and 'PARK.COM', a utility used