Activity Monitor DIsplay

I took delivery of two 27" imacs within a couple of days of each other, one for home and one for the office. One (the office unit) is an i5, the other is an i7. (I had only planned to buy the i7 for home, but we had some uninvited guests go through the office the night before the i7 arrived who took my 4 year old MacPro when they left, so the i5 is a replacement for that machine).

For reasons that I can't figure out, Activity Monitor is acting differently on the 2 machines.

On the i5, when I look at CPU Usage, there is a black window near the bottom of the Activity Monitor window with 4 rows of moving activity monitors in it, one for each CPU core. The dock icon, which is set to display usage, also has 4 columns, one for each CPU core.

On the i7, on the other hand, the black window at the bottom of the main program window shows only one window with what appears to be a single moving graph for the machine as a whole, and the dock icon also shows only one column. There is, however, a separate small grey floating window with 8 "live graphs" in it, independent from the main window. 4 of the graphs appear to reflect the 4 CPU cores, while it is not at all clear what the other 4 graphs represent - they alternate with the 4 that appear to be for the CPU cores, and only show occasional activity.

There was no difference in how the machines were set up - what's the difference here? And what are the other 4 graphs on the i7's little grey window representing?

thanks...Bob