The 100 MHz 12-inch PC Compatibility Card is essentially an entire PC shrunk onto a PCI card (minus drives and power supply), it allows users to simultaneously run Macintosh and PC software as the card has its own RAM, video, sound and processor (an Intel Pentium 100 MHz on this model). The hard disk interface is shared with the host Macintosh introducing a slight penalty in performance.

The card includes a 100 MHz Intel Pentium processor with 256 KB cache, 8 MB RAM onboard (expandable to 72 using 1 64 MB, 70 ns, 168 pin, 5 volt, fast-paged mode DIMM), ATI Mach64 video system with 1 MB of video RAM (expandable to 2 MB using two 256K x 16, 60 ns, 40 pin SOJ package, 5 volt video RAM chips) and a Creative Sound Blaster Vibra 16S sound chip.

Although officially supporting up to Windows 95, the card runs Windows 98 SE without issue. Windows NT and OS/2 are not supported. Operating systems and PC files are stored on a disk image located on the Macintosh hard drive.

Users can switch between the Mac and PC environments simply by hitting command + return, this allows you to easily work on both platforms without one slowing the other down. The card accomplishes this by using a special video cable that connects a single monitor to both the video port on the card and the Macintosh system's video port and switching as needed. A limitation of this is the PC environment cannot share the screen with that of the Macintosh in a window.

Apple also released a 7" long version of this card, which has the advantage of being able to physically fit into computers without a 12" PCI slot and lower cost. To reduce space on the card almost all components were reduced in speed or capacity. Differences between the 7" and 12" cards include 128 KB cache vs. 256 KB, 8 MB onboard RAM vs. 16 MB, 32-bit memory bus vs. the 64-bit on the 12".