Mac ProSource: Apple

What you need to know

  • An interview with Apple's Mac Pro engineers has revealed how Apple keeps its Mac Pro cool.
  • The cheese-grater aluminum case is not just for show, it actually provides 20% more airflow too.
  • Despite the excellent cooling, its fans are reportedly still whisper-quiet.

In an interview with Popular Mechanics, Apple engineers Chris Ligtenberg and John Ternus have revealed some of the tricks Apple is using to keep its brand new Mac Pro super-cool and super-quiet.

Apple released the new Mac Pro yesterday after months of waiting. The Mac Pro is an absolute monster of raw processing power and can be customized to a spec that costs north of $50,000. One of the most touted, or perhaps ridiculed features of the Mac Pro is its "cheese-grater" esque design. Turns out, however, that the holes aren't just for show. In fact, for both the Mac Pro and the Pro Display XDR they provide vital cooling services.

In the interview, Ligtenberg reveals several of the Mac Pro's cooling features, including a very interesting note about Apple's in-house cooling fans:

Ligtenberg's group built the Pro's fan system—three axial fans in the front, with a blower in the back. Since most off-the-shelf fans would be too loud, Apple designs them internally.

"Years ago, we started redistributing the blades," he says. "They're still dynamically balanced, but they're actually randomized in terms of their BPF (blade pass frequency). So you don't get huge harmonics that tend to be super annoying."

Ligtenberg went on to talk about how Apple had borrowed noise-reducing solutions from automobile tires in a bid to create broadband noise instead of total noise. As the name suggests, broadband or wideband noise is noise whose energy is spread out over a range of frequencies, reducing the perception of overall noise, making a sound quieter.

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Alongside Ligtenberg, John Ternus, VP of Hardware Engineering at Apple (who also heads up the Mac Pro and Pro display development) also noted how the pitch of a sound needed to be considered:

"You can have something at a certain SPL (sound pressure) level that sounds really good, but you can have something that's actually at a lower SPL that grates on your nerves and sounds really awful... We want to get really great performance where, you either can't hear it, or if you can hear it, it's kind of a pleasant noise. A ton of analysis goes into figuring out how to optimize for that."

The interview goes on to reveal how Apple ditched noisy fans, even though they often prove advantageous when it comes to keeping out debris because they work well with filtration systems. Instead, Apple has used geometry to minimize the amount of debris that can get inside the computer, and has made those geometries rugged enough to withstand a certain amount of material.

When it comes to the Pro Display XDR, Apple had to eschew normal heatsink fins because the display had to work in both portrait and landscape modes. Instead, it's the bored metal holes that give the Pro and the Pro display their distinctive look that helps to keep the LED panel cool. In the Mac Pro itself, that design also enables about 20% more airflow compared to its ancestor, the Power Mac G5. And it seems to have worked, in his Mac Pro unboxing and quick benchmark rundown Jonathan Morrison said it was "ridiculous" how quietly the Mac Pro was running with all of its cores at full tilt.

The Mac Pro really is a marvel of computer engineering and design, but with a very high price tag, it's aimed at a very specific target audience of professionals who need a lot of processing power, actually, all of the processing power... Let your mind run free and take a look at how much a top-spec Mac Pro will actually cost you.