2. Starting Points

There are several barriers to a Linux for Macintosh 68K port. The first of these is that Apple don't want other operating systems on their machines. Whereas you can learn almost all of the workings of a PC from books you will find almost nothing written on the Apple Macintosh. Sometimes the Macintosh specifications and tech notes fill in the blanks at other times its neccessary to apply a great deal of guesswork and experimentation to figure out the hardware.

The second barrier is a human barrier. Most Macintosh machines were not sold to the technical market, and the average Macintosh user isn't terribly interested in a 'real operating system' for their computer. There is nevertheless a sizeable technically oriented Macintosh user community and a lot of Macintosh hardware around (more probably than any other non Intel Linux platform). A further reason has been provided by Apple whose attitude to 68K machines now appears to be 'quaint, buy a new computer'.

The third barrier to a Linux port is less obvious and is hidden by the lack of documentation. Certain folks have speculated that embarrasment is the main reason for Apple Computer releasing so little documentation. The Macintosh platforms in general have positively stone age design features. For example the interrupt controllers on a Macintosh II are a pair of 6522 VIA chips, intended for use with the 8bit 6502 processor. Stupid hardware makes for poor performance unless carefully handled. The complete lack of DMA is even less helpful. Apple seem to think no DMA is a feature on most machines and actually have a technote 'I used to be a teenage DMA junkie' which attempts to justify their rather comical hardware design.