The entry-level 3.06GHz Core i3 iMac performed very similarly to the 3.2GHz Core i3 iMacs, with the 3.2GHz models averaging between 6 and 7 percent higher scores in our overall system performance test suite, Speedmark 6. Much of that difference, however, was due to poor performance on the HandBrake 0.9.3 encode test.
In our HandBrake test, we encode a chapter of a DVD movie to H.264 with two passes, second pass turbo enabled, and bit rate set to 1500kbps. The 3.06GHz iMac took 3 minutes, 27 seconds to complete the test. The 3.2GHz models finished in less than half the time, completing the task in just 1 minute 37 seconds. We tested and retested and used a different copy of the same DVD and found the same results.
HandBrake 0.9.3 is not the latest version of the software; version 0.9.4 was released just after we finalized our Speedmark 6 test suite. Many readers recommended retesting with the current version of the program—made sense to us, so we tried it. And while we found that 0.9.4 was impressively faster than the previous version, the problem remained. It still took twice as long with the 3.06GHz iMac.
Though I initially assumed that these new iMacs would be using the same SuperDrive model, it turns out that they don’t. The 3.06GHz Core i3 iMac came with an HL DT ST DVDRW GA32N optical drive, which is from Hitachi-LG Data Storage. The 3.2GHz models came with a Pioneer DVRTS09.
To eliminate the optical drive from the equation, we ripped the movie to the hard drive first and then encoded the same chapter with the same settings from the file on the hard drive. In this test, we found both systems to perform pretty much the same, with a difference of around two seconds, instead of 2X.
Putting the SuperDrive back into the equation, we tried another disk test, this time importing a CD into iTunes as MP3s. This took exactly the same amount of time on both systems. Weird, huh? It gets weirder. When we tried to burn the MP3s to an audio CD from iTunes, the Pioneer drive took longer than the HL drive. We did all of these tests multiple times, used the same media, same CDs, etc.
I spoke to one of the HandBrake developers who thought maybe the HL drive uses riplock, where the drive slows down during DVD playback in order to reduce noise from the drive mechanism. If the drive thinks that it’s playing back a movie (and doesn’t realize I’m trying to make a legal backup of the copy-protected movie while holding a stopwatch) then perhaps it’s throttling down a bit for a more silent operation, and thus, affecting the performance.
Of course, you can’t make your buying decision based on what optical drive you prefer. Apple doesn’t specify what brand of optical drive they’ll include, just as it doesn’t specify the brand of hard drives it uses.
New iMacs SuperDrive performance
3.2GHz Core i3
3.06GHz Core i3
Scale = Minutes: Seconds
How we tested. We used HandBrake 0.9.3 and 0.9.4 to encode a DVD chapter to H.264 using 2-pass encoding, with turbo second pass enabled and Quality set to 1500kpbs average bit rate. We used Mac the Ripper to rip the DVD to the hard drive and then used the same settings to encode it using both versions of HandBrake. We imported a 55 minute and 11 second audio CD into iTunes as MP3 with Higher Settings selected. We then burned an audio CD of the songs using iTunes.