Re: architectural goals, Byte Addressability And Beyond

On Fri, 31 May 2024 19:44:49 -0000 (UTC)
John Levine <johnl@taugh.com> wrote:

According to John Savard  <quadibloc@servername.invalid>:

On Thu, 30 May 2024 03:25:14 -0000 (UTC), John Levine
<johnl@taugh.com> wrote:
 

I do not entirely understand why IBM keeps adding special purpose
instructions to z. Maybe it's partly marketing, but they have a
largely captive audience so it has to be more than that. 

>
One possibility is to _keep_ that audience captive even after all the
patents expire that are applicable to machines with the
z/Architecture in its current state, if you are reluctant to believe
that these new instructions genuinely improve performance. 

 
Back in the last millenium there were a bunch of companies that made
clones of IBM mainframes. They all failed. It's the whole ecosystem of
hardware and software, not just individual features that keep the
customers nor patents.
 
I have to say I'm somewhat surprised that IBM has put a lot of effort
into running linux on zSeries, since that's about as un-captive as you
can get. I would imagine that for some kinds of heavily threaded
workloads they could be competitive since the z machines have upwards
of a hundred CPUs with a shared mostly consistent cache.
 

z15 appears to peak at 190/380 User-visible cores/threads.
That's less than quad-socket 56-core Intel Xeon. Quad-socket Xeons
are much less popular than they used to be 20 years ago, but
HP/Dell/Lenovo would still sell you one if you insist.
IBM's own Power System E980 can give you whooping 1536 threads in
maximal configuration.

May be, Telum pulls zArch ahead of those. I don't know much about it.