> this is one of the coolest things I've seen... it's a very modular > architecture; so you just build exactly the computer you need, and when you > want to expand it, you just add more pieces to it. instead of a fixed, rigid > backplane, they use NUMAlink (formerly called CrayLink) cables to go from > brick to brick. makes installation very flexible. Yup. It's really slick. If SGI every discontinued their Origin series, I'd cry. They're really enjoyable machines to admin. > as I understand it; the C-brick has a NUMALink connector, and a XTown > ('crosstown') connector on it. the NUMALink goes to the router brick; and > the XTown goes to the I/O brick. If you add a graphics brick; I understand > that it connects to the I-brick, and from there to the C-brick. > but how do you get decent bandwidth from the CPUs to the graphics unit, > using such a long chain (with possibly 6 feet of cable between each brick)? > Obviously the graphics unit has some pretty impressive onboard GPUs, and a > sizeable cache of its own; but it seems strange to go through an > intermediate unit on the way to main memory. > > or maybe I'm just misreading the product literature. Nope, you've read it correctly. The only to connect the G-brick is via the I-brick. The G-brick needs to be hooked to the I-brick because the I-brick controls the systems console, and once the G-brick is attached, it becomes the console. The G-brick's only connection to the system is via that link. Yeah, it's a bit of a kludge, but it seems to me that it was a sort of 'after the fact' setup. I personally don't think it works all that well. I'd rather have a desk-side Onyx3000 than an Origin with a G-brick (Note: The G-brick is just an Onyx3000 without any 'cpu modules'). Of course, if you need more than 8-16 cpus, then an Origin is the only option, but it's still a PITA to manage, in my experience. Gabe -- Gabe Turner gabe at msi.umn.edu SGI Origin Systems Administrator, University of Minnesota Supercomputing Institute for Digital Simulation and Advanced Computation www.msi.umn.edu