The bug has been opened on https://bugs.launchpad.net/bugs/109356

"Binary package hint: gnome-system-monitor

Hi! This report is about System Monitor 2.18.1.1, running on Ubuntu Feisty. It would be a nice fix for Gutsy.

Currently the CPU History graph in the System Monitor is a nice tool for a quick estimate of the current CPU usage, but only for a very rough estimate. The main problem is that the units are not very clear: the time axis is not marked at all, so I can at most estimate how long a spike took; the height is marked in percent -- but doesn't mention exactly of what.

I'm using Ubuntu on a Centrino Duo laptop, which can change the frequency of each processor according to several factors. (I'm not sure if it can scale each core separately, though. The factors I know are load and whether or not I'm plugged in, there may be some other heuristics.)

All this means that xy % processor usage can mean very different things in terms of how much work the computer is doing. At the very least, the legend below the graph -- [color] CPU#: ##.# % -- should be changed to something like [color] CPU#: ##.# % usage (at ## GHz) -- though this doesn't fix the graph. Maybe a different line (different shade or dotted) could indicate the frequency of the processor."