Disclaimer: while I worked for a DOE supercomputing lab, it wasn't one of the NNSA (nuke) labs, so I don't have all the info. (And even if I did, I certainly wo

Disclaimer: while I worked for a DOE supercomputing lab, it wasn't one of the NNSA (nuke) labs, so I don't have all the info. (And even if I did, I certainly wouldn't be allowed to comment on it.) You're a bit right in that it's more complicated than they say in the article. The power of keeping it up and running is definitely costly, but there's more to it than that. * It takes people to run it. They're expensive, and you don't want your people wasting a lot of time on the old super while your new one is being installed and accepted. I don't recall having seen any plans for a new super at LANL, but there's probably something new showing up soon. * The architecture of roadrunner is outdated and obsolete. The NNSA isn't buying any more, and you can bet that with the new Blue Gene/Q at Lawrence Livermore (sequoia), all their new code is being written for different non-roadrunner architectures. There is considerable cost to porting new code to legacy hardware. * Kind of in line with the last point, sequoia is >17x faster than roadrunner at only 3.5x the power. There's not a lot of point in paying such a premium in flops/watt by running on roadrunner since the new one is already online. * 2.3MW is only what the computer itself uses. There's a ton of other supporting equipment needed to use it (chillers, disk, control nodes, etc.) * This computer isn't being manufactured anymore, so maintenance is going to cost a fortune. When they bought it, they either paid for a hardware support contract or bought a ton of spares and did self-maintenance. If they did the former, IBM is either charging through the nose for replacements or refusing to support it outright. If they did the latter, they're probably running low on spares.