Unusual Usage for CPU Resource Controls

In Hyper-V (and Virtual Server) we allow you to configure a CPU resource reservation, limit and relative weight.  This is usually used for providing performance guarantees for virtual machines – however – last weekend I found a rather obscure usage for this set of settings.

Last weekend there were a number of tests that I needed to run on the RC release of Hyper-V as we were preparing for the formal release.  In order to do this I just grabbed one of my old (slightly dodgy) computers.  After installing Windows Server 2008, and the RC build of Hyper-V, I started setting up a number of virtual machines.

When I was ~80% through guest OS installation the computer spontaneously powered off. 

When I turned it back on the BIOS came up and told me that the system had powered off because I had exceeded thermal limits on the hardware!  After starting up the system again and resuming OS installation I ran for about 5 minutes before the system powered off again due to exceeding thermal limits. 

At this stage it was apparent that my hardware was busted, but I really did not want to have to rebuild on a new system.  So in a moment of inspiration I bought the system up and went through each virtual machine and set the processor limit to 50%.  Once I did this I was able to complete my testing without overheating the computer.

Two hours later – my testing was completed – and a post-it note was put on the physical computer to remind me not to use this computer in the future.