The All-in-One Battle: Dell's XPS One 24 vs. Apple's iMac

The CPU Question: Slow Quad-Core or Fast Dual-Core?

Normally when you compare two similarly priced PCs these days the specs are extremely close. For whatever reason, with all-in-ones, the specs couldn't possibly be more varied. Dell ships all of its XPS One 24s with an Intel Core 2 Quad Q8200 (2.33GHz) while Apple offers either a 2.80GHz or 3.06GHz Core 2 Duo in its 24" iMacs, leaving us with the not nearly age-old discussion of what's better: a fast dual core or a slow quad core?

In the early days the decision was simple, you only gave up a small amount of clock speed if you opted for quad-core over dual (around 266MHz) but in today's comparison the difference is a bit more staggering. The top end iMac gives you a processor that runs its two cores 733MHz faster than the four cores in the Dell, not to mention that those two cores have more cache than is split among four cores in the XPS One 24. Apple's got a higher clock and more cache, but Dell has more cores, so which is better?

Back when AMD introduced its triple-core Phenom parts I put together a little table illustrating the speedup you get from one, two and four cores in SYSMark 2007:

The purpose of the table was to show that while the move from one to two cores is justifiable for the vast majority of users, going from two to four isn't nearly as high yielding. The issue is that while most applications these days are multi-threaded, they are either still bound by the performance of a single thread or they are only able to split the workload two ways, meaning half of the cores on a quad-core CPU would be left with nothing to do. The exceptions are things like video encoding or 3D rendering as you can see from the results above.

To get an idea of general system performance between these two machines I turned to PCMark Vantage, which actually does a good job of comparing similar CPU architectures in a handful of general purpose tests. I'm going to highlight the important tests that really show where these two systems perform the most differently:

The PCMark Memories 1 test is actually a multitasking test with two things happening at once; some basic image manipulation is being performed alongside importing pictures into the Windows Photo Gallery. Both of these tasks are multithreaded and thus there's an actual advantage to having more than two cores, which is why despite the clock speed deficit Dell's XPS One 24 is able to pull ahead.

The Memories 2 test is a simple video transcoding test going from VC-1 to WMV9, and here we see the quad-core advantage once more. The TV and Movies 1 suite also performs a video transcoding operation but this time while playing back a HD-DVD, while both systems are able to play the video back at full frame rate the transcoding task completes faster on the quad-core Dell system.

The TV and Movies 2 test is similar to the one I just mentioned, here we're playing a slightly more stressful HD-DVD source but hitting the disk in an access pattern similar to what would be used in Windows Media Center. Once again both systems pull off the video playback just fine, but the Dell machine is twice as fast when it comes to the disk portion of the test thanks to its extra cores.

The Gaming suites clearly go to the iMac; most games don't use more than two threads and Apple's dual cores are clocked much higher than Dell's four, not to mention that the iMac has a much faster GPU as well. If you want to game, the iMac is the way to go (that still feels weird to type).

The Music 1 test is a light multitasking test, here we're viewing web pages, transcoding a MP3 to WMA format and adding music to a Windows Media Player library. The web task is faster on the iMac, while the other two tasks are slightly faster on the Dell. I'd call this one a wash, the two perform about the same.

The second test is simply transcoding a WAV file to WMA lossless, basically backing up a CD. I haven't seen audio transcoding optimized for more than two threads, so it makes sense that Apple takes the advantage here - the iMac is around 27% faster than the Dell XPS One 24.

The PCMark Communications 1 suite runs three tasks, here we're encrypted data, compressing data and running rules on a Windows Mail inbox. Despite the multitasking nature of the workload, it's simply not heavily threaded enough to stress all four of Dell's cores, Apple takes the clear win here.

The same goes for the 2nd communications suite, it's a 3 task scenario but the iMac pulls ahead in each of the three tasks.

The last two Productivity suites echo what we've seen thus far, take out video encoding/decoding and the quad-core choice just doesn't make sense; a faster dual core wins.

What's interesting here is that there is no clear victory, while I'd venture a guess that the vast majority of users would benefit from the 3.06GHz Core 2 Duo in the iMac, it really depends on your usage model. If you are doing a lot of video editing, video encoding/transcoding and image manipulation - basically if you're using this thing as more of a workstation, then you're better off with the Core 2 Quad Q8200 in the Dell. If you're doing lighter multitasking, general usage stuff or basically anything other than 3D rendering/video manipulation, you'll find the iMac faster - even under Windows. Strange.