On Wed, 18 Jan 2006 16:12:50 -0600, Craddock, Chris wrote: >Let's be clear - there is no difference AT ALL between the engines. >Every engine on the die can execute any instruction defined in the >architecture. > >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 agree that a problem program should see no differences. > >Nope. The only way a zAAP gets to do any work at all is that the z/OS >dispatcher knows a zAAP is there. The dispatcher recognizes JVM work >and, if a zAAP is available, automatically dispatches that work on the >zAAP. But getting it going on the zAAP isn't exactly "free". That's >considered ok because JAVA work is typically going to crank for a >(relatively) long time. ... >On your question of whether you could run an SRB on a zAAP; > >SRBs are intended to be for very short running work that is in and out >and gone. They have been perverted into more long running things (e.g. >DB2) over the years, but the overhead of getting dispatched on a zAAP >would tend to limit the value of running a normal SRB on a zAAP - unless >the system knew ahead of time that the SRB was going to run for a while >- which of course it doesn't. > >In theory if the dispatcher was willing to do it there is no reason SRB >work could not be dispatched on a zAAP, but it would be subject to the >same limitations as the JVM. In practice, the current JVM couldn't run >in SRB mode without some major surgery and there would not be any good >reason to do that. So you won't see an SRB running on a zAAP any time >soon. Why do you say that the overhead is greater to dispatch a zAAP than a non- zAAP CPU? (I'm curious.) -- Tom Schmidt Madison, WI (We have some IFLs and some zAAPs & the they all work quite well.) ---------------------------------------------------------------------- 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
