sunset's gemlog

Synergy: SGI's Lost Itanium System

SGI's family of Itanium supercomputers, the Altix, is well known. Two generations of shared-memory supercomputers were shipped, scaling into the thousands of Itanium sockets and terabytes of RAM. While these massive systems inherited the NUMAlink interconnect family from the slower MIPS-based systems they replaced, they were internally fairly different; the legacy HUB was replaced by a purpose-built SHUB chip, and the Origin's I/O brick fanout ASICs were replaced by the new and powerful TIO. It was not, however, SGI's first attempt at an Itanium system.

In the late 1990s, a project emerged within SGI to support Itanium within the existing Origin platform infrastructure. This project was built around an ASIC called Synergy. Unlike the Altix, which had a new platform infrastructure designed specifically around the Itanium bus and interrupt model, Synergy was a more conservative approach; it was essentially designed to map between a pair of "Merced" Itanium CPUs, sharing a bus, and an otherwise-unmodified Origin platform, including the original Origin HUB and XIO chips. Bringup started in late 2000 or 2001, and aside from one major bug (only one CPU per node worked) the project was essentially successful.

At a late stage of development - after Linux had already booted on Synergy - SGI executives announced at an engineering all-hands meeting that work on Synergy would be ended and future efforts would be based on a new system design, including purpose-built hub and I/O ASICs rather than ones carried over from Origin. This marked the beginning of the Altix project.