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Closer look: Apple Mac Pro unified thermal core, Intel Thunderbolt 2

updated 05:08 am EST, Sat February 1, 2014

Unified thermal core, Thunderbolt 2 make Mac Pro design possible

The Mac Pro (Late 2013) is a perfect example of an electronics product that only Apple can bring to market first. If you look at Apple's current and past product range, it has often been the first to introduce new technologies, new manufacturing processes, and/or custom parts. The Mac Pro features the very latest technologies available for a workstation, new manufacturing processes are used to produce its incredible polished anodised finish, while it features custom logic boards and graphics cards. It is also built around an all-new triangular unified thermal core that we have never seen in a computer before, resulting in its incredibly compact design.

Compared to the model it replaces, the Mac Pro couldn't be more radically different. It is one-eighth the volume of the previous model, it uses one fan instead of eight, and expansion takes place externally instead of internally. It also features dual-GPUs for the first time, and is loaded with the latest and fastest interconnect technology currently available. Apple made these design decisions while completely rethinking what a workstation should be capable of achieving. The previous design dates back to Apple's G5 tower, which was released a decade ago and has only undergone minor external design revisions in that time. A decade is a long time in computing. In that space of time, not only have workstation requirements changed considerably, but Apple has since gone on to become one of the two biggest companies in the world on the back of one breakthrough product after another.

In Apple's vision, a workstation fit for the next decade should be a modular design that allows users to externally expand its capabilities according to their particular needs. Consequently, instead of integrating internal expansion options that users may or may not use, Apple has chosen to drop internal expansion bays. With extraneous componentry out of the way, Apple has then reimagined how the remaining components could be integrated. However, unlike other manufacturers, Apple has never been hindered by the limitations of off-the-shelf components. The original iPhone, the MacBook Air, and the unibody Retina MacBook Pro all debuted with bespoke components that made their breakthrough designs possible. The iPhone featured an incredibly compact motherboard, the original MacBook Air debuted with a custom Intel CPU package, while Apple also pioneered naked SSD and flash drives in its MacBooks, among many other innovations that have made Apple's products stand out for their compact form factors.

Image iFixit

Instead of using multiple heat sinks for the Intel Xeon GPU and dual AMD FirePro GPUs, as other manufacturers do, Apple has built these parts onto a single triangular piece of extruded aluminum that has been designed to maximize airflow and thermal capacity. The unified thermal core is a key component that made it possible for Apple to create a workstation just 9.9-inches tall and 6.6-inches in diameter. A single fan complements this with specially designed blades (to minimize noise and maximise efficiency) that draws air through the bottom inlet, throuagh the core and out the top of the Mac Pro. During our testing, even under intense workloads, we found that the design works flawlessly, quietly blowing heated air out of the unit, while allowing the CPUs and GPUs to work at maximum frequencies.

While the unified thermal core in the Mac Pro is a very clever solution, it is only as effective as it is because Apple has created a custom logic board for the Intel Xeon CPU, and a custom AMD FirePro GPU solution for its Mac Pro. If you look at AMD's regular FirePro workstation GPUs like its W9000, on which the D700 in the Mac Pro is based, you will find that it looks quite different to GPUs fitted around the unified thermal core in the Mac Pro. Where other manufacturers opt for AMD's off-the-shelf parts, Apple has taken the additional step of redesigning the GPUs for the Mac Pro so that it could bring its vision for the Mac Pro to life. While it is arguable that Apple's unique position in the technology work makes the special development of these types of parts possible, it also stands as a testament to Apple's no compromises approach to the execution of its products. This level of development effort takes time and considerable resources, which is what helps to make Apple's products special -- the Mac Pro is no exception.

Mac Pro dual AMD FirePro GPUs

AMD FirePro W9000

Coupled with the design innovation of the unified thermal core at the heart of the Mac Pro design is Apple's use of Intel's PCIe-based Thunderbolt technology, which Apple had a hand in helping to bring to market. Apple was the first manufacturer to debut Thunderbolt technology and continues to push the technology as no other I/O has the same bandwidth. While the unified thermal core helps to make the Mac Pro incredibly compact, it is the Thunderbolt interconnect technology that has allowed Apple to drop the internal expansion that characterized the previous generation. Thunderbolt 2 is backwards compatible with the original Thunderbolt specification, but makes full use of its 40Gbps bandwidth.

Where the original specification combined Thunderbolt's four separate 10Gbps channels in a duplex arrangement that allowed for a maximum 10Gbps bidirectional transfer speed, Thunderbolt 2 bonds the four channels into two 20Gbps bidirectional channels. The good news is that Apple has confirmed with Electronista and MacNN that not only are Thunderbolt devices made for the original specification still compatible with Thunderbolt 2 ports on the Mac Pro (and Apple's Retina MacBook Pros), but Apple's Thunderbolt cables support both the original specification and Thunderbolt 2 speeds. The Mac Pro has six Thunderbolt 2 making it possible to daisy chain up to 36 devices to the Mac Pro. On one chain alone, you can also hook up to six Apple Thunderbolt displays, while you can also connect a DisplayPort device at the end of a six Thunderbolt device daisy chain. Similarly, if you had 36 Thunderbolt devices over the total six Thunderbolt 2 outputs, you could still hook up six DisplayPort 1.2 displays at the end of each chain for a total of 42 supported devices!

However, it is the bandwidth of Thunderbolt 2 that makes it possible for Apple to forgo internal PCIe-based expansion slots. In lieu of these, users who require this type of expansion can use Thunderbolt 2 to add one or more expansion chassis. It gives Mac Pro users incredible flexibility when it comes to tailoring their Mac Pro according to their needs. It also allows the Mac Pro to evolve over time, even if the upgrade path for its internal components is not completely clear at this time. The bandwidth in Thunderbolt 2 also makes it possible for video editors handling RAW 4K Ultra HD video to simultaneously import and backup their data. As an added bonus, the Mac Pro also includes four USB 3.0 ports, which have a bandwidth of 5Gbps.

The Mac Pro is a very powerful and incredibly flexible machine. The combination of the unified thermal core, custom components and Thunderbolt 2 has allowed Apple to craft a workstation unlike anything previously seen. The chances that something like it could have come from any other company are remote. It is yet another example of Apple's uncompromising approach to product design and execution that has made it the undisputed leader in the consumer technology sector.

By Sanjiv Sathiah

by MacNN Staff



  1. iphonerulez

    Dedicated MacNNer

    Joined: 11-28-08

    Wall Street says Apple stopped innovating hardware when Steve Jobs died, so it must be true.

  1. SergioRS

    Fresh-Faced Recruit

    Joined: 09-16-04

    This was probably long in the product pipeline when Steve was around. Fingers crossed for what's to come.

  1. DiabloConQueso

    Fresh-Faced Recruit

    Joined: 06-11-08

    It's like the analysts assume that Steve Jobs was the only smart, creative individual at Apple, and he was surrounded by dull idiots.

    I believe they think that the iPod, iPhone, AppleTV, Mac Pro, iMac, Mac mini, iPad and other Apple products were all brainchildren of Steve's and only Steve, and the rest of the tens of thousands of employees at Apple were just there to be monkeys and make them happen.

  1. Gazoobee

    Forum Regular

    Joined: 02-27-09

    8 fans in the previous model? I see only one and one extra on (some) graphics boards.

  1. OldMacGeek

    Fresh-Faced Recruit

    Joined: 08-04-10

    Gazoobie - look closer. I have fans everywhere in my 8-core Mac Pro.

  1. elroth

    Junior Member

    Joined: 07-05-06

    From a developer's website:

    "Did you know there were actually 5 different fans inside a Mac Pro (early 2009 version)? They are named Intake, Exhaust, BoostA, PCI and Power Supply!"

  1. Gazoobee

    Forum Regular

    Joined: 02-27-09

    So, two people say I'm wrong about the fans, but no one is polite enough to point them out? I'm not spending 40 minutes disassembling my entire desk and computer setup to prove it.

    Mid 2008 Mac Pro. There is one giant fan at the front and one on the add-in graphics card. So ... two, (or one if you use the original graphics card). The next model added one more fan no? Where are the rest?

  1. Mechanic

    Fresh-Faced Recruit

    Joined: 12-11-11

    Actually there are 4 fans not including the graphics card fan. Each Mac pro has two very large fans in the front, you can look through the front grill and see these, and one very large fan at the bottom in the back. The lower front fan is the processor input, the lower large rear fan is the processor exhaust fan, the upper fan in the front is the pci cooling fan, and the 4th fan is hidden, it is in the middle behind the dvd drive bay and cools the power supply. The 3 large fans you can see from the outside of the case by looking through the grill. The 4th you can't. When you include the gpu fan there are 5. But the gpu fan is on its pci card.

  1. Mechanic

    Fresh-Faced Recruit

    Joined: 12-11-11

    you can look at a 2009 mac pro here torn apart and see the fans.

  1. Mechanic

    Fresh-Faced Recruit

    Joined: 12-11-11

    All original mac pros from 2006 to 2012 models have 4 main fans and one graphics card fan.

  1. Sanjiv Sathiah

    MacNN Staff

    Joined: 06-05-13

    This is a quote from the official Apple Mac Pro Reviewer's Guide:

    "Cooled by a single fan versus eight in the previous generation, Mac Pro is as quiet as a Mac mini at idle, at just 12 dBA."

  1. mac_in_tosh

    Forum Regular

    Joined: 12-14-11

    Maybe someone can explain. From the price of this computer, it is obviously aimed at professionals. As a non-pro, I have previously bought G4 and G5 desktops but no way would I consider spending over $3M for a computer and no display. But does a professional really car how his tool looks? Would a pro not prefer a simple, easily opened box with similar components? It seems this MacPro is making use of commercially available components for the most part so much of the effort has gone into the form factor.

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