slow network game

i have a question i have a new mac,
Processor 2.9 GHz Intel Core i7,
Memory 8 GB 1600 MHz DDR3
Graphics Intel HD Graphics 4000 512 MB
Software OS X 10.8.2 (12C3012)


my brothers is
Processor 2.5 GHz Intel Core i5
Memory 4 GB 1600 MHz DDR3
Graphics Intel HD Graphics 4000 512 MB
Software OS X 10.8.2 (12C3012)


his game is running so slow on a network game. we both previously had a lap top do we need to do anything to speed it up.
or why is his running so slow.
thanks