OSDev.org

Have you tried it? What do you think?

that looks like a great tool, but probably not well suited to hobby OS development and certainly out of price for the poor lil' us ...

..

http://www.virtutech.com/products/simics.html

it's a system simulator, which looks targetted on performances and multi-plattforms simulations.

Unlike bochs and vmware which are targetted to the sole PC systems, simics seems able to simulate SPARC workstation/servers, and other large and expensive systems (IBM servers ?) that you usually cannot afford for testbeds ...

there is an old simics version that is GNU or something.. then after that it went mega $$$$$$$$$$$$$$$$$$$$.....

you can still find the linux source version around the traps...
how it compares to its commercial cousin i dont know...

SIMICS is very good. if your [un]lucky enough to be a student or academic you can get it on academic licence with no restrictions, although I think you do have to buy it eventually or get relicenced for it. Ive beem using it about 4 months now and foun dit very useful, especially teh debugging tools, however the one problem I have found is that sometimes the code works slightly differently in SIMICS and on bare hardware from boot up, so its worth testing your code to make sure it works as planned in both.