IBM finishes Cumulus rollout

With a 24-core SMT-4 processor an option for the Talos systems, you can be forgiven for forgetting these beasts come even bigger. Let's look at IBM's recent announcement of the the last of the POWER9 herd.

The Sforza modules in the T2 and T2 Lite are Nimbus systems, with four-way symmetric multithreading and support for up to two processors (so-called "Scale Out"); the currently largest 24-core variant thus has 96 threads per processor and therefore a maximum of 192 per system. These PowerNV systems are designed to run an OS on the bare metal and have "direct attached" RAM that does not require a memory buffer. By contrast, the Cumulus ("Scale Up") systems come as SMT-8 parts, and support up to sixteen processors. Notably, the current maximum core count is "only" twelve, so the maximum number of threads per processor is still 96, and the Cumulus systems use Centaur memory buffers which act as a level of cache below L3 and offer about half the memory bandwidth of Nimbus. On the other hand, this also allows shops with big IBM investments to use the same RAM from their POWER8 machines, a substantial cost savings, and the "Fleetwood" Power E980 with all 16 processors enabled offers a staggering 1,536 threads. The Cumulus machines are also designed to boot and run AIX, IBM i or Linux virtualized under PowerVM, whereas Linux is the only supported option for the Nimbus machines.

The smaller of the two machines, though they're both beefy, is the 4U "Zeppelin" Power E950, which supports four processors and comes in 8, 10, 11 (?!) and 12 core variants running from 3.1 to 3.8GHz, thermal headroom permitting (the 8-core has a base frequency of 3.6 and the 12 core 3.1), for up to 384 threads. A 16Gb/s NUMA interconnect links the processors and up to 16TB of RAM is supported. It supports AIX and Linux.

The 5U "Fleetwood" Power E980 is basically up to four E950s lashed together with 25Gb/s Bluelink between the nodes, with four times, well, everything. And you can bet that includes the price tag. The (up to) 192 cores are also slightly faster, ranging from 3.55 in the 12-core processors to 3.9GHz in the 8's. The E980 is the only system of the two that supports IBM i, as well as AIX and Linux.

Obviously there will be future POWER9 systems as well as these, but this completes IBM's current roadmap. Read more about it at TheNextPlatform.