On Mon, Oct 29, 2018 at 1:33 PM Rick Stevens <ricks@alldigital.com> wrote:

Do big IBM (or any) mainframes still exist?

You can still buy S/390's, but the big money is not in mainframes, but in supercomputers. It used to be (in the days of Seymour Cray) that a supercomputer just had a really fast processor that could do vector processing (running the same instruction on a whole block of memory locations in parallel in a single clock tick), but we have pretty much gotten to light speed limitations on how fast a processor can be, so  IBM's supercomputers these days are clusters of thousands of processors and cores, exchanging data over specialized high-speed fabrics such as Infiniband.  Linux is critical to making this work (as well as specialized application libraries to support interprocess communication on such as system). The IBM supercomputers I have seen all use a variant of Red Hat Linux, so I wouldn't be surprised if acquiring Linux developers might not be the main reason for IBM to want to buy Red Hat.

--Greg