> >zAAP engines are a slightly different specialization. They are not > >visible in the normal scheme of things and they can't field (I/O) > >interrupts.
> Is this "they can't" because of the contents of control register 6, or > because of something else? I am not really sure. At some level the I/O interrupt mask has to be off, but the key question is where is that set? Don Deese said that the personality of the cpu is set in the HSA by PR/SM as part of LPAR dispatch. That has the ring of truth about it because among other things, it wouldn't require the overt cooperation of the operating system. z/OS and zVM are both more aware of their environment than zLinux - which basically doesn't care what the engine is. > Why do you say that the overhead is greater to dispatch a zAAP than a non- > zAAP CPU? (I'm curious.) Well for one thing, when the dispatcher is running on a normal CPU it is already running on the engine where the application code will be dispatched. There is a separate (not externally documented) signaling protocol to get work fired up on a zAAP. Even on its best day that is going to entail more path length than an ordinary dispatch. CC ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
