Multi-Processor Usage an Lubuntu 13.10 (64-bit) on MacBook

[Aere Greenway]

All:

After installing Lubuntu 13.10 (64-bit Mac) on my MacBook, I notice an 
anomaly with respect to multi-processor usage.

I installed gnome-system-monitor (because I like the graph showing 
internet throughput).

On using it on other systems, when it's on a multi-processor system, it 
shows a CPU-usage graph-line for each available processor.  But in this 
case (even though it has two processors), there is only one CPU-usage 
graph line.

When I checked the "System Tools"..."System Profiler and Benchmark" 
tool, it showed that it is a dual core (2 processor) machine, and that 
each processor has a speed of 2 gigahertz.

Yet when I later ran Qsynth on it (where it was configured to use 
PulseAudio, rather than JACK), there were cut-outs in the sound, 
suggesting that perhaps it is only using one processor.

So I am wondering if the Gnome System Monitor is actually correct in 
showing only one processor?

If so, why does the System Profiler show that it is a dual-processor?

-- 
Sincerely,
Aere