You could do your own pipe lining XR something else.. ... ST
I suspect we are having an academic discussion rather than practical. I suspect most of the time will be in other areas, such as which cache the storage region is in. In a loop, the second time you issue the request is likely to be faster than the first time, because of cached instructions, data location, TLB etc. I remember a performance person normally got consistent results within 1% when he had the CPUs on one chip. One day the systems on the CEC were IPLed in a different order, and so he got his CPUs on 2 chips. The results were about 5% different! Colin On Tue, 10 Feb 2026 at 04:40, Pieter Wiid <[email protected]> wrote: > With XR/STH, the STH will have to wait for the XR to complete, so it may > not be faster > > On February 9, 2026 9:57:43 PM GMT+02:00, Seymour J Metz <[email protected]> > wrote: > >If I had to do it on an old machine before MVHHI then I'D use XC for > clarity. I suspect that the XR/STH is the fastest of your three. > > > >-- > >Shmuel (Seymour J.) Metz > >http://mason.gmu.edu/~smetz3 > >עַם יִשְׂרָאֵל חַי > >נֵ֣צַח יִשְׂרָאֵ֔ל לֹ֥א יְשַׁקֵּ֖ר > > > > > > > > > >________________________________________ > >From: IBM Mainframe Assembler List <[email protected]> on > behalf of David Clark <[email protected]> > >Sent: Monday, February 9, 2026 1:48 PM > >To: [email protected] <[email protected]> > >Subject: Half-word Counter in Storage -- Best Practice > > > > > >External Message: Use Caution > > > > > >If a half-word counter has to be in storage (to save on registers) and > must > >start at zero, which is better or which would you prefer to do as a best > >practice? > > > >...simply clear storage? > > > >XC STRGLEN,STRGLEN FOR USED STRING LENGTH COUNTER > > > >...or clear a register and save to storage? > > > >XR R5,R5 STARTING AT ZERO > >STH R5,STRGLEN SET USED STRING LENGTH COUNTER > > > >...or use an immediate value and save to storage? > > > >LHI R5,0 STARTING AT ZERO > >STH R5,STRGLEN SET USED STRING LENGTH COUNTER > > > >Sincerely, > > > >Dave Clark > >-- > >int.ext: 91078 > >direct: (937) 531-6378 > >home: (937) 751-3300 > > > >Winsupply Group Services > >3110 Kettering Boulevard > >Dayton, Ohio 45439 USA > >(937) 294-5331 > > > > >
