Apple's MacBook Pro: Using it as a Mac and a PC

Power Consumption and Performance per Watt

Compared to the G5, Intel's Core Duo has no problems offering lower power consumption, but what about when pitted against the G4? The whole reason the G4 was kept in Apple's notebook lines was because of its low power consumption; while the Core Duo can easily be a better mobile CPU than the power hungry desktop G5, how does it compare to an already low power G4?

First off, I measured idle power consumption of the entire notebook at the wall outlet. The battery was removed from both notebooks so we're only testing the power consumption of the computer + display.

At idle, the PowerBook G4 running at 1.5GHz manages to come in at 21W total system power consumption, a full 3 Watts lower than the Core Duo 2.0GHz system. The number of variables between the two systems are really too many to count, thus making it difficult to declare this a clear victory for the G4 processor over Core Duo, but it does mean that the older PowerBook G4 notebooks consumes slightly less power as a whole at idle than the newer MacBook Pros.

Next, we ran our QuickTime H.264 encode test and looked at peak power consumption under full CPU load. Keep in mind that QuickTime's H.264 encoder is multi-threaded so both cores are under full load in the MacBook Pro:

Under full load the PowerBook G4 jumps up to 40W while the MacBook Pro falls 3W short and peaks at 37W, giving us a role reversal. It looks like although the older G4 systems consume less power at idle, the MacBook Pro is greener under full load. Of course low power consumption itself is meaningless if you don't have the performance to back it up (remember Transmeta?). Now let's look at the performance per Watt in the previous test.

What I did for this graph was take the average frame rate during the H.264 encode task and divided it by the peak power consumption during the test thus giving us performance measured in frames encoded per second, per Watt.

Using QuickTime's H.264 encoder as our benchmark, the new MacBook Pro offers around 62% better performance per Watt than the previous PowerMac G4. For a notebook, that sort of increase in performance per watt is extremely important.

Interestingly enough, despite the relatively similar power consumption characteristics the new MacBook Pro uses a noticeably larger AC adapter than the PowerMac G4 rated at 85W instead of 65W.