What’s Inside the New Mac Pro?

Apple has used innovative design on this new compact desktop computer


Think Different” was an Apple slogan from a few years ago. And the company has done that, especially when it comes to design, producing a string of computers and tablets that have different approaches to design. The new Mac Pro is a great example of this, and with this innovative product now going on sale for delivery by the end of the year, we wanted to find out what is it that makes this product different? The answer is all inside the case of the new Mac Pro….

The new Mac Pro was announced at the same June event as the iPad Air, where Apple VP Phil Schiller dismissed suggestions that the desktop computer market lacks innovation. “Can’t innovate any more, my ass” he smirked while unveiling the Mac Pro to oohs and ahhhs from the audience. And the Mac Pro is certainly unusual, packing a state of the art desktop PC into a circular case under 10 inches high and 6 inches wide. That is smaller than the power supply used on some high-end Windows computers

The Technology Remains The Same

The new Mac Pro is just 9.9 inches tall/ and weighs 11 pounds / Apple

While the design of the Mac Pro is unusual, the components inside it are not. Apple uses the same parts as other computer makers: a single Intel i7 processor running at 3.7GHz with between four and eight cores, up to 64GB of fast DDR3 memory and dual workstation AMD graphics chips. That’s all standard, off-the-shelf stuff that you can configure on any high-end PC from a custom retailer. The difference is that most Windows PCs that use these high-end components are massive, monolithic systems that can be used as a desk themselves, filled with whoosing fans that push air through the system. By comparison, the Mac Pro is miniscule, with just a single fan inside the top of the case. That means the Mac Pro is quiet: Apple claims that it produces an incredibly low 12 dBA at idle, and under 20 dBA while under load. A typical Windows with a similar spec would produce a lot more noise: the SilentPC website reviewed a PC case that was designed to be quiet, but which produced about 35dBA when under heavy load. (However, we should note that dBA numbers are notoriously finicky to measure, and Apple didn’t disclose how theirs were arrived at, so it’s hard to draw a real comparison).


It’s All About the Heat

So what is the magic secret that Apple uses to make the Mac Pro quiet? There are two parts to it: splitting the computer into three parts, and a big hunk of Aluminum that sits between them.

Most computers are composed of two main parts: a motherboard that the processor and memory are attached to, and the expansion boards that fit into the slots on the motherboard. These expansion cards are things like the graphics cards and other devices that add functions to the computer.

The anatomy of a typical PC, shown without case / Original photo by Flickr user Sven

This standard design has been in use for over 20 years, and is the basis for most computers. However, it has some issues. Putting the expansion cards at right angles to the motherboard makes it awkward to mount the heat sinks and fans that cool the components. As you can see from the typical layout above, there are seperate heat sinks for the processor, for the graphics card and for the components on the motherboard, with several fans (not all shown; some are built into the case) pushing cool air over these heat sinks.

What Apple did was to throw out this design and start from scratch. They split the computer into three separate circuit boards: one for the processor and memory, and two for the graphics cards, with one GPU on each.

The three circuit boards of the Mac Pro, with the two graphics boards (left) and the processor and memory board (right)

These three circuit boards are placed around the heart of the design: a large extruded Aluminum heat sink. The hot components of the computer (the processor and graphics chips) are placed against this heat sink, so their heat spreads into the heat sink. Above this heat sink is the single fan, which draws cool air from the base, past the heat sink and out of the top. Combined with the natural tendency of hot air to rise, this puts all of the heat produced by the computer into a single heat sink, which is more efficient.

Apple’s own diagram of the heat flow inside the Mac Pro / Apple

Computers produce a lot of heat, and the Mac Pro is no exception. The Intel processor used by Apple can generate up to 130 watts of heat, while the two AMD FirePro graphics chips (which are functionally similar to this graphics card) can each suck down over 270 watts of power, which ends up getting expelled as heat. Combined, that is a maximum of something in the region of 670 watts of heat that has to pass through the heat sink and into the air that exits the case. That’s about as much heat output as this wall-mounted electric heater.

Cylinders Are the New Cubes

So will it work? Apple has tried designs like this before, such as the Mac G4 Cube, which was released in 2000. Although this computer looked great, it was notorious cracks in the clear polycarbonate case, caused by both manufacturing problems and overheating. Apple killed this design in 2004.

A Mac G4 Cube (on right) with monitor and keyboard / Flickr user Mac Minimalist

The Mac Pro is a different beast, though, with a metal construction that conducts heat better, and the addition of the large fan. So, it is unlikely to have the same issues, although it remains to be seen how noisy the system really gets when it is working hard to edit 4K video.