OK, so I'm curious. MPs were available at the same time asAPs, IIRC. Was MP support strictly a VM/HPO feature? Base MVS 3.8 works on AP/MP systems just fine. My first sysprog job was on a 370/158AP running?3.8, and we did get a performance boost?when we added the AP.
On Mon, Oct 31, 2022 at 8:12 AM Bob Polmanter <
wably@...> wrote:
AP support is available in VM/370? (not MP), but I wouldn't recommend bothering with it.? Because of the limitations where the attached processor cannot do i/o, it forces a lot of extra overhead onto the main processor.? Unless you have just the right mix of work loads, there is little benefit to using AP support.? You would need to have a lot of CPU-bound workloads that do little i/o in order to get any real benefit.
Basically, I found that performance is no better than running in uniprocessor mode.? It's no worse, but you simply don't 'feel' the benefit of having an extra processor.
With that said and at the time not aware of the lack of performance, I did go through the drill of getting AP to work on VM/370 R6.? This was using the Sixpack 1.2 system sometime around 2016.? I documented the effort and the steps to generate an AP nucleus as well as some bug fixes to CP in order to get it to run AP; those materials are in the files section of this group called 'ap.zip'.? This could be made to work on VM/CE but probably would not work right out of the box because VM/CE has had a lot of maintenance and changes since Sixpack 1.2 of 2016.
I don't recommend even bothering because of poor performance of AP.? Worse, if you run AP you must turn off ECPS:VM which drags performance down even more.?? But if anyone has any interest and wants to dig through it and see what they could do with it, the files are there for those so inclined.
Regards,
Bob
