Post by Dennis Boone Post by David Wade
I believe that its the other way round. zOS is carefully rigged so it
"normally" won't run on an IFL. There used to be options to licence bits
that normally don't run on an IFL on an IFL....
My understanding is that the "rigging" is to remove one or two
specific instructions from the architecture on an IFL, and make
sure the z/OS depends on using those instructions.
Some non-definitive documentation implies that is the case:-
Integrated Facility for Linux® (IFL)
This is a normal processor with one or two instructions disabled that
are used only by z/OS®. Linux does not use these instructions and can be
executed by an IFL. Linux can be executed by a CP as well. The
difference is that an IFL is not counted when specifying the model
number of the system. This can make a substantial difference in software
This is mis-information....
Well lets look at the definitive "Principles of Operations". This is the
bible for what the hardware does. (you will need an IBM ID to read this
but they are free)
it goes into great detail on how to test the processor type but no where
does it mention any difference in the instructions implemented.
This is odd, because if there were differences, you would need to know
them to write assembler, and its perfectly possible to write Assembler
on Linux, some kernel components are assembler. So if an IFL is
different you would expect it to be in the manuals.
Then lets look at the Z14 technical guide...
This explains that if you order for example a Z14 Model 01 it comes with
33 CPUs. You can have any combination of "Normal" and IFLs (and some
other speciality engines) up to the 33 that are installed in the box.
What you get depends on how many licences you buy. The rest sit there as
so you can start with just 1 "Normal" CP and run zOS. If you want more
CPU power for zOS you send IBM money and they send you some new
"licenced internal code" (lic) that lets you define an extra "Normal"
CPU. If you want Linux you can send less money and IBM will send you new
LIC for one normal and one IFL. You continue with any mix up to the
limit of the box. Any not used are considered "spares"....
... page 109 says...
All PUs on a z14 server are physically identical. When the system is
initialized, one integrated firmware processor (IFP) is allocated from
the pool of PUs that is available for the entire system. The other PUs
can be characterized to specific functions (CP, IFL, ICF, zIIP, or SAP).
The function that is assigned to a PU is set by the Licensed Internal
Code (LIC). The LIC is loaded when the system is initialized at
power-on reset (POR) and the PUs are characterized. Only characterized
PUs include a designated function. Non-characterized PUs are considered
spares. Order at least one CP, IFL, or ICF on a z14 server.
This design brings outstanding flexibility to z14 servers because any PU
can assume any available characterization. The design also plays an
essential role in system availability because PU characterization can be
done dynamically, with no system outage.
so while the introductory guide says instructions are disabled none of
the technical documentation documentation supports this. It specifically
says all chips are identical at the silicon level.