[Info-vax] CentOS has been effectively killed for production use

[David Wade]

On 10/12/2020 15:23, Dennis Boone wrote:
>   > 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.
> 
> De
> 
Some non-definitive documentation implies that is the case:-

https://www.ibm.com/support/knowledgecenter/zosbasics/com.ibm.zos.zmainframe/zconc_mfhwPUs.htm

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 
costs.

This is mis-information....
... why

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)

https://www-01.ibm.com/servers/resourcelink/lib03010.nsf/0/B9DE5F05A9D57819852571C500428F9A/$file/SA22-7832-12.pdf

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...

http://www.redbooks.ibm.com/redbooks/pdfs/sg248451.pdf

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 
spares.

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...

 >>>>>>>>>>>>>>>>
3.5.1 Overview

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.

Dave
G4UGM