The Mac Pro Review (Late 2013)
by Anand Lal Shimpi on December 31, 2013 3:18 PM ESTThunderbolt 2
The new Mac Pro integrates three Intel Falcon Ridge Thunderbolt 2 controllers. These are the fully configured controllers, each supporting and driving two Thunderbolt 2 connectors on the back of the Pro for a total of 6 ports.
Pairing Thunderbolt 2 with Ivy Bridge EP is a bit tricky as Apple uses Thunderbolt 2 for display output as well as data. Typically you’d route all display through processor graphics, but in the case of IVB-EP there is no integrated graphics core. On a DIY PC you enable display output over Thunderbolt 2 by running an extra cable out of the discrete GPU and into a separate input that muxes the signal with PCIe and ships it out via another port as Thunderbolt. Here’s where Apple’s custom PCB work comes in handy as all of this is done internal to the Mac Pro. The FirePro’s display outputs are available via any two of the six Thunderbolt 2 ports, as well as the lone HDMI port on the back of the Mac Pro.
How does Thunderbolt 2 differ from the original? For starters, it really would’ve been more accurate to call it Thunderbolt 4K. The interface is fully backwards compatible with Thunderbolt 1.0. You can use all previous Thunderbolt peripherals with the Mac Pro. What’s new in TB2 is its support for channel bonding. The original Thunderbolt spec called for 4 independent 10Gbps channels (2 send/2 receive). That meant no individual device could get access to more than 10Gbps of bandwidth, which isn’t enough to send 4K video.
Thunderbolt 2 bonds these channels together to enable 20Gbps in each direction. The total bi-directional bandwidth remains at 40Gbps, but a single device can now use the full 20Gbps. Storage performance should go up if you have enough drives/SSDs to saturate the interface, but more importantly you can now send 4K video over Thunderbolt. Given how big of a focus 4K support is for Apple this round, Thunderbolt 2 mates up nicely with the new Mac Pro.
So far I’ve been able to sustain 1.38GB/s of transfers (11Gbps) over Thunderbolt 2 on the Mac Pro. Due to overhead and PCIe 2.0 limits (16Gbps) you won’t be able to get much closer to the peak rates of Thunderbolt 2.
The impact of chaining a 4K display on Thunderbolt 2 downstream bandwidth
Here’s where the six Thunderbolt 2 and three TB2 controllers come into play. Although you can daisy chain a 4K display onto the back of a Thunderbolt 2 storage device, doing so will severely impact available write bandwidth to that device. Remember that there’s only 20Gbps available in each direction, and running a 3840 x 2160 24bpp display at 60Hz already uses over 14Gbps of bandwidth just for display. I measured less than 4Gbps of bandwidth (~480MB/s) available for writes to a Thunderbolt 2 device downstream from the Mac Pro if it had a 4K display plugged in to it. Read performance remained untouched since display data only flows from host to display, leaving a full 20Gbps available for reads. If you’re going to connect Thunderbolt 2 devices to the Mac Pro as well as a 4K display, you’ll want to make sure that they aren’t on the same chain.
If we start numbering in the top left corner of the 2 x 3 array of Thunderbolt ports and go left to right down the stack, you'll want to first populate ports 1, 2 and 5 before filling in the rest. The diagram below should help simplify:
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Anand Lal Shimpi - Tuesday, December 31, 2013 - link
Behind the multithreaded curve, the two are almost identical :)Calista - Tuesday, December 31, 2013 - link
It seem to follow the multithreaded graph perfectly, a tiny bit of a blue graph can be seen in the upper right corner. So it's actually hidden by the second graph.japtor - Tuesday, December 31, 2013 - link
One thing I keep forgetting to ask since it hasn't been mentioned anywhere, does AirPlay display spanning/mirroring work? I figured it used QSV on the other Macs which this machine doesn't have, so just curious if they just left it out completely.skiboysteve - Tuesday, December 31, 2013 - link
I wonder if they changed it to AMD hardware encode...Calista - Tuesday, December 31, 2013 - link
So not really a proper upgrade for anyone owning a Mac Pro from the last few years unless Thunderbolt, faster GPU or a small form factor is needed.Anyway, it's an impressive package and it's clear Apple have brought with them a lot of the knowledge they have gained over the years building laptops.
Lonyo - Tuesday, December 31, 2013 - link
Indeed. As was the question with the "super thin" iMac... what's the point?It's all very well having a super small computer blah blah, but in this instance, for this type of machine and end user, what's the real benefit?
The cost has gone up for a base model, performance per dollar has gone down compared to the previous one, there's no ability to upgrade GPUs.
As soon as you start plugging in Thunderbolt devices, there goes your "sleek looks" etc. Plus it's more expensive to get a Thunderbolt HDD/etc than just stick one inside the case, further increasing costs.
Yes, it looks nice, and from an engineering standpoint it's very well done, but... is it really the right product for the market?
Calista - Wednesday, January 1, 2014 - link
For anyone not planning on bringing the computer with them from time to time it's certainly not a very practical design. Desktop-space is often more highly valued than floorspace, and lack of upgrade paths are obviously a con.But for those with a need to bring a powerful computer with them on a set or similar it's a much more practical solution as compared to the previous design. I think Apple was quite aware what they were doing. A complete field setup with a 27" monitor, the Mac Pro, cables, keyboard and mouse is less than 20 kg. Much more than a laptop for sure, but still a fairly acceptable weight.
Lonyo - Wednesday, January 1, 2014 - link
Wouldn't it make more sense to have TWO designs then? A Mac Pro for people who need portability, and a Mac Pro for standard single location users...?I mean, I know Apple tends to be all about deciding what the consumer wants for them and removing choice as much as possible, but sometimes that's not the best way.
akdj - Wednesday, January 1, 2014 - link
Why doesn't this model fit that mold? For the stay at home/office/studio...one can easily AND reasonably tie thunderbolt storage together in a very acceptable and aesthetic way. Whether it be a drive enclosure...set of enclosures, TB docks that are now available adding more USB 3/HDMI/audio/et al I/O....who needs a huge box for slow internal 3.5" HDDs anymore? These PCIe SSDs tear the 2.5" models apart. Inside the 'old' style MP, a 'new' GPU on X16 takes up two slots! Sure doesn't leave much room for your MIDI, PCIe SSD or external pro sound card!I'm amazed at how few 'get it' here anymore. Especially after such an exhaustive review. I'm a bit biased as I make my mortgage and have for 22 years doing audio and video production. From hauling reel to reels, vinyl, film and racks of around and lighting gear to rMBPs, iPads (now with fill 64 channel wifi front of house control with Mackie) and this new Pro....I've shaved thousands of pounds from load ins and outs. Same in the camera realm. Working the last seven years with Discovery and it's subsidiaries in Alaska, I can't put into words what this machine means to us. And it's ability to pay itself off many times over just in the course of a year. Exciting times. Hopefully an evolution Win OEMs will consider as well. Shouldn't be any moving parts any longer. Wait and space are ALWAYS an issue. As is the price of power....the advantage of speed, and software developers following suit to unload computational crunching to the GPU
nunomoreira10 - Tuesday, December 31, 2013 - link
Now there just need to be a dual cpu single gpu offer to please everybody.