How Microsoft's Surface Book compares to Apple's MacBook: Let's play CPU detective

On the Surface, Microsoft's Surface Book may look like hype, but here's why it's an engineering stunner.

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Microsoft clearly had Apple’s MacBook and MacBook Pro in its sights when it designed its radical Surface Book. But was it marketing hype or was Microsoft really laying down legitimate smack when it said the Surface Book offers “twice” the performance of a comparable Mac?

It very much depends on the hardware that’s inside the Surface Book. There’s not much public information on the exact parts inside the Surface Book—but we do know what Microsoft is claiming.

Let’s play hardware detective

By adding the discrete GPU, two extra processors, it fundamentally makes Surface Book two times faster than the MacBook Pro,” said Microsoft VP Panos Panay during Tuesday’s unveiling.

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Despite the company saying the Surface Book had “two extra processors” it’s likely the device has a dual-core CPU inside.

What Panay meant by the “two extra processors” statement isn’t totally clear, but I would interpret that to mean Surface Book has a quad-core chip.

All of Apple’s MacBooks are dual-core Broadwell-based CPUs with integrated graphics. Moving up to the MacBook Pro 13 doesn’t change much either. The Pro still has a dual-core Broadwell CPU with Intel integrated HD 6100 graphics. Apple also oddly limits these MacBook Pros to Core i5 chips (with slower graphics chips) in it's ready to buy, but does offer the Core i7 as an option with faster integrated graphics.

Even more maddening, the Microsoft store for ordering the Surface Book doesn’t provide any clarity on silicon features (it’s a very Apple-like move). The spec pages—which should indicate which CPU you’re getting—doesn’t reveal anything. All you can divine is that you’re getting a 6th-gen Intel Skylake CPU in either Core i5 or Core i7 trim.

There are still a few details I can suss out of the Surface Book, though. The lowest-end version will feature a Skylake Core i5 chip with Intel 520 graphics. That means the bottom-end Surface Book is likely going to have one of two CPUs inside: A Core i5-6200U or a Core i5-6300U, as those are the only two chips with that graphics core.

This also tells me that Microsoft’s claims of the Surface Book walloping the MacBook Pro likely aren’t based on the lowest-end Surface Book unit.

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The green rectangle in the center is the Intel Skylake CPU. Up left, there’s an M.2 PCIe drive, and just to the right of the Skylake CPU is the DDR3L RAM.

Skylake is better but...

Skylake is certainly a better processor than Broadwell, but I really don’t think the mobile version will offer twice the performance of Broadwell laptop, based on all my testing of the desktop parts. There’s a lot more nuance to what defines “speed,” and Skylake offers a lot, especially on mobile. But if you’re being truly honest, and looking at this question core-for-core, Skylake doesn’t boast twice the performance of a Broadwell CPU. That’s like claiming your iPad Pro is faster than 80 percent of portable PCs.

But then there’s the Core i7 model of the Surface Book. What chip is in that? I don’t know. But it’s likely Microsoft is hanging its “two times faster” performance claims on the Core i7 version, which could possibly, conceivably, be a quad-core chip.

It’s not unprecedented, after all. VAIO stuffed a quad-core Haswell CPU into its Surface Pro clone targeted at professionals. You can read about that engineering feat here, where I note that heat, noise and battery life will be a challenge in the VAIO Z Canvas.

If Microsoft chose to put a quad-core Skylake chip in it the Surface Book, it would likely be one of three Intel CPUs that you can peep at here. The problem is all three are rated for 45 watts—which gives them about three times the power and thermal footprint of a dual-core processor. That level of power consumption and heat generation would be pretty hard to pull off in such a thin body.

The next step down is Intel’s newly announced Core i7-6820EQ, which drops power down to 28 watts, but even that wattage is hard to imagine in the Surface Book.

There are a few things that work in Microsoft’s favor, though. Skylake should be a much cooler CPU than the Haswell quad-core in the VAIO Z Canvas. The Intel quad-core chips can also be tuned down to lower frequencies to keep heat under control. But the odds are good that there’s a dual-core Skylake chip in the Surface Book, and not a quad-core chip.

So if it’s a dual-core, could the Surface Book still be twice as fast as the MacBook Pro? Yes and no. It all depends on what you’re testing, and what benchmarks you use.

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The undisclosed Nvidia GPU inside is the magic here. No modern 13-inch ultrabook-class laptop I know of packs discrete graphics.

Discrete graphics for the win

The icing on the Surface Book is the use of an undisclosed Nvidia graphics chip. Microsoft lists it as “8G” and the official press release docs say it has a piddly 1GB of GDDR5 RAM. But in the land of integrated graphics, the 1GB frame buffer and discrete graphics is king. In the thin Ultrabook class, which the Surface Book technically falls into, discrete graphics are typically unheard of these days due to power consumption and thermals. None of the MacBooks have discrete graphics, and neither does the MacBook Pro 13.

I’m betting Microsoft is hanging its performance claims on the graphics acceleration offered by the GPU. One demo, for example, showed the Surface Book editing a video in Premiere Pro CC, which heavily leans on the GPU. That’s easily enough to justify Microsoft “2x” claims.

Realistically, though, unless Microsoft did stuff a quad-core chip inside the Surface Book, the MacBook Pro will perform pretty close to the Surface Book in more conventional CPU tests such as Cinebench R15.

That doesn’t mean Skylake or the Surface Book is a slouch. There’s a lot under the hood in Skylake that offers better performance than previous-generation processors. Skylake, for example, offers fixed-function encoding and decoding of 4K that would make a Broadwell or Haswell CPU plain choke. That includes Broadwell-based PCs and Macs. 

If Skylake runs cooler in the Surface Book, it also means it can run at higher frequencies for longer periods, and this too could help it outpace the MacBook Pro. But by a 2x margin? I’m very skeptical, and only testing will tell the whole story.

The upshot is the Surface Book with its discrete GPU and dual-core Skylake chip (probably, right?) is likely to be the fastest laptop when it arrives—depending on how you use it.

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The GPU in the base is essentially an external graphics setup. The array of batteries around it in the tablet section get the laptop to 12-hours of battery life.

Why the Surface Book is truly radical

But let’s not ignore the real engineering achievement here, as it can be easily overlooked. With the Surface Book, Microsoft puts the CPU, M.2 drive and system RAM in the tablet portion of the computer. Meanwhile, the Nvidia GPU is housed under the keyboard.

That means the Surface Book essentially uses external graphics. That’s not a huge deal as Alienware uses this in its laptops and you can hack a system like this together as well.

The real big deal with Surface Book is the ability to decouple the external keyboard (along with its GPU) and have it automatically switch over to the integrated graphics. None of the external graphics solutions I’ve seen allow you to do that. Instead, you must reboot.

Clearly, Microsoft has worked some special magic with Intel and Nvidia to enable a hot-swap of the running graphics. The good news is Microsoft usually shares the technology, so there’s a good chance this will bubble up in other, non-Microsoft hardware too. 

Microsoft also gets to explore improved thermals by stuffing the graphics in the keyboard instead of the tablet body. The GPU has its own dedicated cooling system separate from the CPU, so both parts can’t heat each other up. This should, in theory, let Microsoft run the CPU at higher temps than a design that has both a GPU and CPU in the same shell. 

One other question I’m really interested to have answered is whether you can buy the Surface Book without the graphics chip and then later buy the keyboard combo with the GPU and essentially upgrade it.

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Remarkable: You don’t have to reboot when disconnecting the base from the graphics chip.

But let’s cut back to the original question: Is the Surface Book twice as fast as the MacBook Pro 13?

I think it’s fair to say that in Premiere Pro, which you can run on both operating systems, Surface Book will probably be much faster. And in other other tasks that can be run on both platforms—say, a Handbrake encode that uses Skylake’s 4K hardware circuits—it’ll also beat down the MacBook Pro by a healthy margin too. And in games, even with its limited 1GB of graphics memory, it’ll also ace the MacBook Pro. 

So, yes, based on these types of comparisons, I judge Microsoft’s claims to have merit—with the caveat that not every single application will be faster on the Surface Book. But at least Panos Panay’s audacious statement has more merit than Apple saying the new iPad is faster than 80 percent of portable PCs.

Correction: An earlier revision of this story didn't note Apple does offer Core i7 in its Configure To Order MacBook Pro 13s. Also clarified Microsoft's positioning against the MacBook Pro 13.

This story, "How Microsoft's Surface Book compares to Apple's MacBook: Let's play CPU detective" was originally published by PCWorld.

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