To multicore or not to multicore

It's possible to use the non-multicore kernel on a multicore box. In this case, only processor 0 will be used; the other processors won't run your code. This is a waste of additional processors, of course, but it does mean that you can run images from single-processor boxes on an multicore box. (You can also run SMP-ready images on single-processor boxes.)

It's also possible to run the multicore kernel on a uniprocessor system, but it requires a 486 or higher on x86 architectures.