The U.S. Navy has completed a program to upgrade the sonar systems on all of its nuclear submarines. The A-RCI (Acoustic Rapid COTS Insertion) program involved more than installing faster computers and more memory. That's because COTS stands for "Commercial off-The-Shelf". That means the sonar gear was modified so that it can more easily take advantage of new processors and memory developments. Since these items have been doubling in power, every 18-24 months, for over 40 years, it's about time. In the past, submarines often had sonar systems powered by decade old CPUs, and memory chips that were no longer manufactured. Fortunately, the navy is not alone in running ancient gear, so there were suppliers who bought up old CPUs and memory SIMMs, and sold the stuff to the navy. Sometimes, however, particularly old components could only be found on eBay.
The navy began the A-RCI program in 1998, but it has taken over a decade to debug the system and get the gear into 44 subs, as such major modifications could only be done when the boats came in for refueling (usually halfway through their careers) or for some other major repairs or maintenance. The new Virginia class boats have A-RCI built in.
Sonar, particularly the passive (just listening) type, depends heavily on computer processing power to detect and identify anything out there.