Bride of Frankenmac revisited: How our OS X PC compares against an iMac

Macworld Lab recently cobbled together the Bride of Frankenmac, a PC that runs OS X. One reader pointed out that our choice of processor and components wasn’t close enough to the specifications of the Mac Pro that we used for our performance comparisons. We used a Mac Pro as baseline because we thought that with the upcoming Mac Pro’s closed design, some people might be tempted to make their own updated mini-tower system that has plenty of room for internal upgrades like PCI cards and storage devices.

Looking around the lab, I found a Mac system more in line with the Bride’s specs—a late 2012 27-inch iMac, configured to order with the same quad-core 3.4GHz Core i7-3770 processor as the Bride of Frankenmac, a 1TB Fusion drive, 16GB of RAM, and Nvidia GeForce GTX 680MX graphics with 2GB of video memory. All told, this custom iMac is $2799.

We gave our Bride of Frankenmac a makeover, outfitting it with a 1TB Fusion drive that used an OWC 240GB Mercury Extreme Pro 6G SSD ($295) and a 1TB WD Caviar hard drive ($90). Matching the graphics card between the Bride of Frankenmac and the Mac was a bit more challenging, as the iMac uses the MX version of the Nvidia GeForce 680, which is meant for mobile graphics. Since Nvidia’s 600 line has been discontinued and replaced by the 700 series, we couldn’t get a loaner GeForce 680 from the company. Instead, we ran our tests on both an EVGA GeForce GTX 760 ($250), as well as the EVGA GeForce GTX 770 ($410). The total cost of these Bride of Frankenmac configurations came to approximately $1363 with the GTX 760 and $1523 with the GTX 770.

Fusion drives are available as a configure-to-order option on iMac and Mac mini models. They combine an SSD and HDD into one logical volume. Data is copied first to the SSD portion of the volume and moved to the slower hard drive section later. It’s really cool technology that gives you the speed of an SSD with the capacity of a hard drive. We’ve written a how-to article on making your own Fusion drive, and if you’re not averse to spending a little time with the command line, it’s a pretty straightforward process for creating one for a Mac.

But using a Fusion drive on our Frankenmac was a little less straightforward. We found instructions on the Web that guide you through transferring OS X from an already operational OS X/PC to an already configured Fusion drive. We were able to get that far easily enough, but we did run into problems booting from the Fusion drive directly. I’m confident that we will eventually solve our issue, but for the sake of timeliness, we decided to take the easy route and use the bootloader from the existing hard drive to boot onto the Fusion drive.

Once we had our two systems configured as closely as we could, we ran our Speedmark suite of application tests to see how the two compared in terms of performance. The CTO iMac was 7 percent faster, overall, than the Fusion-powered Bride of Frankenmac with the GeForce GTX 760 graphics card installed. The iMac’s Fusion Drive was between 9 and 12 percent faster in our large file copy, zipping and unzipping tests. Curiously, the iMac’s GeForce GTX 680MX was able to push more frames per second in Cinebench’s OpenGL test, but was not able to keep up with the 760 graphics in our Portal 2 tests at highest settings, which ran nearly 20 percent faster on the Bride. Switching out the GTX 760 for a GTX 770, showed this more expensive graphics card to be an even better performer; this card was able to display 9 percent more frames per second in our high-resolution Portal than the less expensive GTX 760. We also ran the Heaven and Valley graphics benchmarks and found the 760 to be 15 and 17 percent faster, respectively, than the internal 680MX graphics in the iMac. The GTX 770 was 22 percent faster than the GTX 760 and 42 percent faster than the iMac’s graphics.

We know that installing the Mac OS on anything other than Apple hardware breaks the OS X end user license agreement (EULA). But that’s not the only reason to be cautious about building your own Mac. It can also be a technical challenge, depending on the parts you choose to use. While many people claim the process to be relatively smooth and painless, we’ve heard others complain of quirks similar to what we found when building our Bride of Frankenmac. But easy or hard, legal or not, the comments we received show that the topic of DIY Macs is of great interest.

Have more ideas for our Bride of Frankenmac? Let us know in the comments.

Next page: Complete test results.

Bride of Frankenmac: Individual application test results (Speedmark 8)