The and G7 platforms are very similar, they both have the same CPU socket and memory. The motherboards that have G6 CPUs can mostly be upgraded to G7. The difference between a G6 and G7 is purely the CPU. We know that the next CPU that will be in the G8 will be a new socket type, so all G8 servers will be new servers.

Intel releases a new CPU socket every two years(ish) and so if you buy a new server, you can normally upgrade the CPU once, then its another new server. So you end up with a yearly upgrade cycle as follows:

New Server - New CPU - New Server - New CPU - New Server - New CPU

The G6 and G7 use the following CPUs

  G6    E5-2680 V3 (12 Physical Cores)    G6 1U = 1052 / 2U = 2052
  G7    E5-2697 V4 (18 Physical Cores)    G7 1U = 1052 / 2U = 2053

At the time of writing (Dec 2016) v7 is just being released, and this runs on both the G6 and G7 servers, but you need to know what version of CentOs to run, the chart below explains this.

  Platform        G6              G7
  
  MFEL            V6 and V7       V7 Only
  
  CentOs          v6.7 or v7.2    V7.2          (or above)

The G7 platform has around 30% more processing power than the G6, so has much better density.