> As for the ISA, Intel seems to be very "ad hoc" compared to the z > architecture. Especially in the virtualization arena. Basically, > the z has a _single_ virtualization instruction: SIE. > Intel has I don't know how many different versions of different > instructions to let hypervisors run at all. I don't > know how efficient vitualization actually is on Intel. > But it wouldn't surprise me if it were a pig.
As far as I know, the biggest advantage z/ has over Intel (and many others) is the wait state. It is sometimes difficult for virtualization to figure out when the guest isn't doing anything. Most other systems use a null process with a small loop, while waiting for an interrupt. (But if you know you are running virtual, there might be some way around it.) I beleive that the wait state came from the days of usage meters, when the meter would stop while the processor was waiting. If not for rentals of S/360, it might not have had the wait state. -- glen
