My machines are single proc P4's running between 1.4 and 3Ghz with 512-1Gb of ram. Not dual cores, but not slow pokes either.
Note also that in my setup, any given single DB instance genenerly only contains on average about 1000 bots. The 10,000 number is the total across the 10 connected instances.
Note that many performance elements of DB are non-linear w.r.t. bot population. That is, a sim with 500 bots will run more than twice as fast as the same sim with 1000 bots all else being equal. Said another way, two connected instances with 500 bots each will run faster than a single sim with 1000 bots, all else being equal. The computation necessary for things like vision, bot-bot collision detection and bot-shot collision detection have artifacts that go up polynomially with population, non linearly, especially if there are lots of bots in close proximity.
Even in a given sim with a constant population, the sim will run as much as 2X slower or even more if all the bots are clumped together as opposed to spread out across the sim. This is becuase if two bots or a shot and a bot are close enough to possibly collide or see each other, etc. over the next cycle, then certain performance shortcuts in the code cannot be used and the actual, expensive calculations must be performed. By using multiple instances, no code needs to execute to check for collisions, etc. between bots in differnence instances. Thus, the overall computation load for the total population is less than it would be for a single instance.
My topology between the 10 instances is a ring and generally self regulates, spreading the population out fairly evenly as the field sizes are not large and thus if the population in any single instance goes up, the increased density tends to increase the outbound teleportation rate over time.
If you suspect a performance problem with the program, I would be very interested in taking a look at a sim which exhibits slower performance in recent versions than in prior versions...