The Apple II Clone inside an IBM PC
By 1985 the Apple II had continued to gain greater popularity in the personal computing markets. With the recently released Apple IIe, the 8 bit system moved from strength to strength. However the 16 bit IBM PC with its greater power and capability had grown over the past four years to become a popular system, which may have enjoyed an accelerated market uptake due to the recent entry into the market of a large number of South East Asian companies producing clones of the system at very competitive pricing. As a result, several companies entered into a niche market of developing peripheral cards to allow Apple II compatibility on a PC. One of the first and maybe more popular cards was the Diamond Systems TrackStar card. This card was built on an ISA or MCA based IBM PC expansion card and brought to the PC full Apple II/IIe compatibility. Depending on which model of card you bought, would depend on which Apple system you would be compatible with. Diamond Systems eventually produced four models of the Trackstar card.
The primary reason we look at the Trackstar board in relation to the soft Apple FPGA is purely to get a better understanding of the system. The Trackstar card is in essence an Apple Clone with some extra fancy logic to provide an interface to the ISA bus and to pass Apple II data in a format both the PC and its peripherals can understand. One of the more interesting aspects of the design is the fact that it has two 65C02 processors, which may have broken Apple compatibility at the logic level and replaced its functionality through emulation. The designers put in a solid effort to not only create an interface to the PC, but also to enable full compatibility up to an Apple IIe using just standard PAL's and GAL's. For most other cloners, ripping off the MMU and IOU as they were was the preferred approach. It is these characteristics of the design that make it so interesting to study. The photos below were provided by a work colleague who once owned one of these cards, but unfortunately let it go. I am grateful he took some quality pictures of the board for his ebay auction, as they give a good insight into what the card comprises of. Hopefully over time, we may be able to get our hands on some schematics and a ROM set for study purposes. In the meantime, it makes a great example of how far the Apple clones made their way into other systems.
Trackstar is an example of a technology that was applicable to the era it was conceived in. By having a foot in both the Apple and IBM camps, the design was susceptible to going out of date very quickly. As both IBM and Apple evolved in different directions, the usefulness of the card diminished. IBM left ISA and DOS and Apple went to 65C816 and ProDOS. Although Trackstar is a very interesting design, it is not the sort of thing that would have any benefit in running today, even if you could locate an historic PC that had all the right characteristics to enable it. As an example of two systems in one, it's a great study tool primarily because it is expected that future FPGA based designs will be configured as "many in one" systems, most likely using old 8 bit systems to prove the concept. However this time, the concept will be structured around a more a modular approach. One that allows truly independent upgradable faithful copies to co-exist within a single device, using transceiver blocks inside the FPGA to provide bridging and exchange services between each of the complete systems and common peripherals.