Beowulf systems are commonly built from Intel-based PCs or DEC Alpha
based workstations, since these are usually most cost effective for
building dedicated compute clusters.
iMacs and
Power Macintoshes
using PowerPC G3 processors have become quite popular as desktop machines,
but Pentium-based PCs have better price/performance, particularly
for floating point intensive scientific applications.
However these machines could be a useful compute resource if they are
already available within an organisation, for example as
desktop computers or in a teaching laboratory.
Apple computers have not generally been used for cluster computing due to the limitations of the MacOS operating system. However, with the advent of LinuxPPC, a native port of Linux to the PowerPC, it is now feasible to do cluster computing with iMacs. We have created a prototype iMac Beowulf cluster using LinuxPPC. We used release 4.0 of LinuxPPC, which is still fairly immature, so some of the applications we tried did not work as well as expected. We have also tested release 5.0, which only fixed some of the problems. Parallel computing using Linux on iMac clusters is still problematic, however they can be used to farm out batch jobs using cluster management software such as DQS or Condor. This work is described in more detail in a technical report.
The next release of MacOS, MacOS X, should be available for the iMac in early 2000. This will be an interesting development, since it offers a BSD Unix API that should be able to support cluster computing software while still running a MacOS interface.