Suspend Quartus processing

[Altera_Forum]

How can I suspend Quartus (9.0 sp2) compilation process? 

It seems I can only interrupt it and then I need to restart from beginning. If I need to use the computer a little while for another task during compilation I must face long delays: the pause-restart function would be very helpful.  Another question: if I change only pin or timing assigments in a design, is it mandatory that Quartus needs rebuild the entire project from scratch? I expected some tasks could be skipped (i.e. analysis and synthesis) since design logic has not changed.  Regards

[Altera_Forum]

There is no way to suspend it, sadly. Note that you can go to Tools -> Options -> Processing and tell Quartus to run as a lower priority thread. For a single CPU machine this is great, since it keeps things like email/internet very fast, but allows Quartus to run in usually the same amount of time. The only downside is if you run something else compute intensive, like a modelsim simulation, it will completely hog the CPU.  

For the second one, Assignments -> Settings -> Compilation Process -> Smart Compilation will try to skip modules that can be skipped. It's not perfect though. You can also go to Assignments -> Design Partition Window and set the top-level partition to Post-Synthesis, which tells it to skip synthesis when it can. I don't think this is available in web edition versions though. Finally, note that synthesis is now timing driven, so technically a timing assignment should require all modules to be re-run. It's probably fine to skip synthesis in most cases, but something to be aware of.

[Altera_Forum]

i requested a pause feature once. i think the explanation was that it would be difficult to implement, getting to a "safe" stopping point and dumping all of the RAM contents to disk. 

 i have used Quartus in a virtual machine to "pause" the compilation by putting the VM into a "saved state".

[Altera_Forum]

That's correct pancake. The VM method is a good one if you don't mind the ~3% compilation slowdown running Quartus II virtually. It's easier for the VM to dump the contents to disk since it's performed at a higher level layer managed by the VM software.