There are analogue targeting computers on naval ships that still work, and work quite well. Deck guns that can fire a Volkswagen Golf-sized projectile from (say) Hobart to any tennis court in Launceston. Maybe not the best economical solution, but what's money to the military, anyway?
Point is, you look at the system, and determine whether you can support the subsystem that drives it. As an integrated system it either works or it doesn't, irrespective of the weight, the cost, or the paint job on any subcomponent of it. And sometimes the bit that the computer controls is just as old and slagged-out as the operating system driving it.