On Nov 30, 2015, at 5:44 PM, J O Skip Robinson wrote:
I'm reaching back a long way to stretch the notion of
'straightforward', but here goes. When I was a novice sysprog, my
shop had an Amdahl. MVS at that time predated 'system product'.
(Way back.) IBM shipped a new level of MVS that executed
instructions not present our Amdahl. Amdahl responded by shipping
some code that was loaded early in IPL to accommodate the new
instructions. The code would trap a S0C1, determine if it were a
new instruction, and if so, 'fix' it. Some instructions were
considered unnecessary; others needed to be simulated. Unnecessary
instructions were NOOPed in memory; a simulated instruction was
replaced in memory with a direct branch to the simulation routine.
As time went on after an IPL, there were fewer and fewer S0C1s to
deal with.
So what about taking a similar approach with an all-architecture
product? Write it to run on the latest hardware and trap the S0C1s
that occur on older hardware, then simulate the unexecutable
instruction with something 'traditional'. Whew. Sounds like a lot
of work, but you would have a truly universal product.
---------------SNIP-------------------
Then there is the "other" story. A well known southern university
were being told that they had to go AMDAHL. The manager cooked up a
program that ran poorly on AMDAHL and the IBM it ran perfectly (of
course).
They used that justification to pick IBM.
Ed
----------------------------------------------------------------------
For IBM-MAIN subscribe / signoff / archive access instructions,
send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
