For many pro applications, the most powerful Mac computer you can buy today is not the $5,000 iMac Pro. The best Mac you can buy today is not new and not even sold by Apple—it’s six years old and is sold by a third-party company in Denmark.

There is a small but growing community of creative professionals—video editors, audio engineers, software developers, 3D modelers, and graphic artists—who are modifying their circa 2009-2012 Mac Pros to be even more powerful than the ones Apple sells today. Because those computers can use top-of-the-line graphics cards that aren't compatible with the iMac Pro or the 2013-and-onward Mac Pro, these modded computers are crushing the benchmarks of even brand new new computers.

The Mac Pro 4.1 and 5.1 are known in the community as the “cheese grater” Mac Pro towers. These are the last highly upgradeable and modifiable desktop computer that Apple sold before moving to the much-maligned “black trash can” design that is sold today and hasn’t changed significantly since 2013. Upgraded versions of the 4.1 and 5.1 are, in many cases, the fastest Apple computers you can buy today.

People are putting new CPUs, RAM, SSDs, and modern graphics cards in the cheese grater Macs that are, in many cases, superior to what you can buy from Apple today. The Facebook group Mac Pro Upgrade is filled with people scooping up old Mac Pros from eBay and Craigslist and modifying the hell out of them.

“We’re using the skeleton of the machine,” Gianluca Mazzarolo, owner of the Denmark-based Big Little Frank, which makes custom Mac Pros for creative professionals, told me on the phone. “With CPUs, nothing drastic has happened in [the last 3-4 years]. To do what a lot of pros want, you just need a good GPU. We’ve found a way to put two good ones in old Macs. For some things, it’s better than any Mac offered at the moment.”

"We’re helping the company close this huge stopgap between 2013 and whenever they introduce the new Mac Pro"

There are pitfalls: Installing new CPUs sometimes involves “delidding” a processor, which means removing a shield from it to make it compatible with the 4.1 or 5.1. Certain newer components are not compatible because drivers don’t exist. The lack of Thunderbolt ports makes doing this a nonstarter for certain people. Mazzarolo also has had to find a way to reroute the Mac Pro’s power supply to directly power electricity-intensive modern GPUs (as designed, the power is routed—and limited—by the computer’s motherboard.)

Image: Big Little Frank

But many of these potential problems have been completely solved by the community. Like the Hackintosh community, the Facebook group has a running list of compatible and incompatible parts, shares written and video tutorials about upgrading the computers, and has even found a way to upgrade the Mac Pro 4.1 into the Mac Pro 5.1 with a firmware update. As an end-around the lack of Thunderbolt Port, people are using 10 Gb/s ethernet connections to directly connect their computers to massive hard drives that store media.

Big Little Frank’s business is aimed at the “pro” community who feels like Apple let them down by killing the upgradeability of the MacBook Pro and Mac Pro.

“It feels completely ridiculous to be doing this. You cannot go to Apple.com and find a computer better than these,” Mazzarolo said. “I think a lot of people in this group see upgrading the Mac Pro as a cheaper way to get a functional Mac. But I don’t think the point is really the essence. The essence is people wanted more powerful Macs and Apple didn’t give it to them, so we are.”

Various people have been experimenting with their own DIY Mac Pro upgrades, and lots of YouTubers are sharing methods for upgrading the computers.

Mazzarolo is right that there is a wide sect of Apple’s customer base is upset with the fact that it hasn’t updated the Mac Pro since 2013, and new MacBook Pros are both unupgradeable and have only USB-C ports to expand with. Last year, Apple went on a press tour to let the pro community know that the Mac Pro is not dead—but a new model hasn’t yet been announced. In response to this gap in the market, the Hackintosh community has thrived and the Mac Pro Upgrade community has risen.

There are a few reasons why older Mac Pros can become so powerful:

Even though cutting-edge CPUs don’t work with them (the drivers often don’t exist, and in some cases the six-year-old motherboard can’t handle them), the Mac Pro 5.1 was designed to accommodate up to 12 cores: “Even though a single core isn’t fast, imagine having 12 of them for video editing and audio—those cores together are faster than my brand-new MacBook,” Mazzarolo said. The new iMac Pro can have up to 18 cores; new MacBook Pros max out at four cores.

The 5.1 can take a whopping 128 GB of RAM, which is equal to what a fully upgraded iMac Pro can take and double what Apple says the trash can Mac Pro maxes out at (it’s worth noting that the RAM used in newer Mac computers is usually faster)

The 5.1 can be modified to use modern SSDs, which Mazzarolo said are in some cases faster than the ones used in the new iMac Pro

The 5.1 can use almost any brand-new graphics card from most manufacturers, which is the main reason why a fully souped-up, old Mac Pro can outperform new computers. “With some rendering engines, the AMD cards that Apple uses [in new Mac Pros] don’t even work,” he said. “In general, even mid-level graphics cards we put in are as fast as those in the iMac Pro. We can put in better cards and we can put in two of those.”

On the Facebook group, Mazzarolo posted benchmarks of one of his custom-built rigs playing 5K, 6K and 8K RED RAW video clips against current-model Apple computers. A new, 15-inch MacBook pro and a recent “trash can” Mac Pro weren’t capable of playing the video at more than 8 frames-per-second. His custom-built model was able to get 24 fps in each case.

Image: Mazzarolo

To be clear, even the most highly modified Mac Pro 5.1 will not be able to outperform newer computers in many day-to-day tasks. These modified computers are specifically made for video editing, graphic design, and audio recording and editing, and many of Mazzarolo’s clients work in those industries. I’ve seen people trying to play brand new video games on some of these older machines, for instance, and they have had wildly unpredictable results.

Mazzarolo also knows that his line of work won’t exist forever. His machines vary in price from $1,500 up to $9,000 (which includes separate external hardware for specific clients.) He tells clients that his computers will likely be competitive for another couple years, and that it will no longer make sense for him to modify these computers in about a year and a half as CPU and RAM technology in stock computers improves to the point where the components that are still compatible with old Mac Pros can no longer compete.

He, like everyone else in the pro world, is anxiously waiting for Apple to announce new Mac Pros. Until they come out, he says he’s doing Apple a favor by keeping people from switching to PC in the meantime.