The north bridge is a chip on your motherboard that communicates with the CPU and other major systems on the board. The south bridge is a second chip that communicates with the north bridge to communicate with more peripherals than just the north bridge can handle.
These are chips built into the motherboard and not changeable unless you replace the board. If there is a question linux related, we need more information to help you.
Looking at the data, it seems as if the AMD 880G chipset is a damp squib - AMD has literally dialed the 785G up a notch and slapped on a new number. As you can see from the results, only when AMD fiddles with how the game is rendered does it actually make a big difference, with other games showing no or only slight speed improvements. Worse still, the driver hacks for Trackmania made it look like we are playing it on a SNES.
The boards still support the same Socket AM3 CPUs as before, yet since most 785G boards support the latest Phenom II X6 6-core CPUs anyway, and the features of the chipset haven't been upgraded, there's very little point ditching a 785G mother for an 880G one.
It could be argued that the SB850 Southbrdige is the biggest benefit, with its SATA 6Gbps and RAID 5 support. Previous 785G boards were almost always paired with the SB 710 Southbridge that offered neither of these features.
Realistically though, SATA 6Gbps currently has little benefit for hard disks, which struggle to saturate SATA 3Gbps connections. Meanwhile, compatible SATA 6Gbps SSDs cost ten times as much as cheap 880G motherboards, so are an unlikely upgrade. We'd ignore the RAID 5 support too, as RAID rarely offers much if any increased performance and isn't as robust a backup method as an external drive on or an online service. If you do value both or either of the core benefits of the SB850 Southbridge, remember that a lot of 880G board won't use it, so check the specs before buying.