The LHC was completed in 08. That chip was sold from 06 to 12. This means basically half the pc's they bought ~15 years ago are still meeting their needs.
Honestly, this is the way it should be. The only reason most enterprises upgrade their computers is because Microslop, and all the other proprietary software they've allowed themselves to grow dependent on, require it; not because a 20 year old computer isn't snappy on Debian, or isn't powerful enough for email, docs, and browsing. The LHC requires supercomputers and server farms for primary operations. These pc's are basically just thin clients to access those resources.
There are still a shocking amount of Windows XP and 7 systems in production, because the software stack doesn't need to be updated. If those systems had been deployed on linux 20 years ago, they would still be fully capable of receiving security updates.