Hats off to Alan. He has, again, come through with a sensible answer, and a bit of history. Our MVS guys confirmed that there was no such thing defined in their world (but I would wager that they can, at most, vary n-1 cpus off of a system that has n).
Regards, Richard Schuh > -----Original Message----- > From: The IBM z/VM Operating System > [mailto:ib...@listserv.uark.edu] On Behalf Of Alan Altmark > Sent: Thursday, December 10, 2009 3:42 PM > To: IBMVM@LISTSERV.UARK.EDU > Subject: Re: Base Processor? > > On Wednesday, 12/09/2009 at 08:20 EST, "Don W." <thisus...@yahoo.com> > wrote: > > When you set up the directory entry for a z/OS guest with multiple > virtual > > CPU's (e.g. CPU 00, CPU 01) and you QUERY CPUS, CPU 00 > shows as BASE. > What > > is the difference between a BASE CPU and a non-BASE CPU? Does it > > really > make > > any difference in this environment. In terms of real processors, at > > one > time > > the base processor had to do the I/O. I do not believe that is true > > any more. Am I correct? and when did that stop being the case? > > The "base" CPU is the first CPU that is defined to your > virtual machine. > What it really means is that you can't DETACH it, since every virtual > machine must have at least one virtual CPU. Otherwise the term is > meaningless. > > Each processor has always been able to do its own I/O. What > changed (370 > -> XA) was the introduction of a "channel subsystem" that enabled any > processor to get to any device. Prior to that, each CPU had > its own set of channels. I/O to *that* device had to be > scheduled on *that* CPU. Now we're all one happy family! > > Alan Altmark > z/VM Development > IBM Endicott >
