On: Mon, Dec 04, 2006 at 02:24:39PM -0800,Schuh, Richard Wrote:
} IIRC, the times for SR and XR were the same on the Amdahl machines, at
} least on the ones that came after the 470. They may have been the same
} on the 470, as well.
I do recall that on the Amdahl 470s, there was one pair of instructions
which were often executed together many places in VM/370 where the order
of which one was first mattered a lot for execution time. They could go
in any order, but the IBM code usually executed them in the wrong order
for the 470s. A large fraction of the Amdahl mods to run VM 370 took a
sequence like:
xx .....
yy .....
and changed that to:
yy .....
xx .....
to squeeze out a few more microseconds of performance.
I don't recall what difference (if any) the instruction order made on
blue hardware.
--
Rich Greenberg N Ft Myers, FL, USA richgr atsign panix.com + 1 239 543 1353
Eastern time. N6LRT I speak for myself & my dogs only. VM'er since CP-67
Canines:Val, Red, Shasta & Casey (RIP), Red & Zero, Siberians Owner:Chinook-L
Retired at the beach Asst Owner:Sibernet-L
