Hardware is also only as useful as the supporting software which exists for it. The wide range of support for PC hardware under the Linux operating system is what makes the total combination of Intel hardware and Linux an attractive package. We also choose our hardware (network cards, graphics cards, etc.) based on whether properly written Linux drivers exist. With the wide selection of hardware available, we can afford to do this easily, and still end up with very cost effective solutions.2
For data acquisition, Unix has been the environment of choice at CFHT for many years. On the Intel machines, the 2.2 Linux kernel is an extremely stable platform, and interoperates well with our existing Sun and HP machines which are running Solaris and HP-UX. To the end user, there is truly no difference in using a Linux environment today as compared to any other modern Unix. Linux likely will, and largely already has become the standard Unix. (Such statements caused mixed and mostly skeptical reactions a few years ago, but are now being taken more seriously.) Even though Unix itself may be ``old'', nothing better has come along yet for the job we do. Most of our older machines are now being replaced by Intel/Linux. The figures in the previous section illustrate a target which will probably be reached before the end of 2002.
Our Detector Hosts run a special version of Linux called RTAI Realtime Linux. This is a hard (deterministic) real-time operating system which was required to handle the strict requirements of reading out MegaCam's controller. RTAI Realtime Linux lacks some of the features of a real-time operating system like OS9 or VxWorks, but it provides exactly what was needed for MegaCam (deterministic response in one place in an interrupt handler.) Moreover, it lacks none of the features of regular Linux. From a programming and maintenance standpoint, the single difference is the Detector Hosts boot a different kernel image file.