The InterMapper polling engine is single-threaded, so nearly all work done by intermapper.exe/intermapperd is restricted to a single CPU. Adding more CPU is not helpful in the case a single-threaded (vs multi-threaded) architecture.

No combination of CPU/RAM will allow InterMapper to monitor more devices once it reaches its limit. Choices are to poll less often (longer polling interval), monitor fewer interfaces/device on average for SNMP probed devices, change the probe mix to use more lightweight probes (like ping/echo), or to expand to an additional server by shifting some of the maps (chart data continuity can be a problem in this case).