The GPU Comparison

If you had asked me last year I would've told you that Apple clearly values GPU performance more than CPU performance—and I wouldn't be far off the mark. Apple went to great lengths to use the best of the entry level GPUs and paid no mind to the fact that the 13-inch MacBook Pro, Mac mini and MacBook Air all used much older Core 2 Duo CPUs while the competition was busy shipping Core i3/5/7s.

This year is the year of the CPU however. The entire MacBook Pro lineup gets Sandy Bridge CPUs and as a result they all get Intel's new HD Graphics 3000. Here's a die shot of Sandy Bridge:

Note that the GPU core is integrated on-die. There are actually two versions of Intel's HD Graphics available on Sandy Bridge, but all current mobile versions of SNB come with the 3000 model. What does the 3000 offer you? Twelve scalar execution units (EUs) running at a base clock speed of 650MHz. The GPU can also turbo up depending on available TDP. The max frequency is somewhere between 1.2—1.3GHz depending on the processor SKU.

Being basically desktop replacements, the 15-inch and 17-inch MacBook Pros also include a discrete GPU. This round they both use AMD hardware and the options are below:

Discrete GPU Options
  AMD Radeon HD 6490M AMD Radeon HD 6750M
Manufacturing Process 40nm 40nm
SPs 160 480
Texture Units 8 24
ROPs 4 8
Core Clock 800MHz 600MHz
Memory Bus Width 64-bit 128-bit
Memory Clock 800MHz 900MHz
Frame Buffer 256MB GDDR5 1024MB GDDR5

The entry level 15 uses a Radeon HD 6490M while the upgraded 15 and the 17 both use a Radeon HD 6750M. The difference between the two GPUs amounts to compute horsepower, memory bandwidth and available frame buffer. With only a 256MB frame buffer the 6490M is insufficient for high performance at larger resolutions (courtesy of an external display). The 6750M is paired with 1GB of GDDR5 and thus has no problems smoothly driving a 27-inch 2560 x 1440 panel. The new GPUs now only use a x8 connection to the SNB CPU compared to the x16 from last year's models. Remember Sandy Bridge has a x16 PCIe controller on-die. The controller can be split into two x8s or 1 x8 and 2 x4. In this case one of the x4 ports is used for Thunderbolt, leaving 4 unused lanes and a x8 for the GPU. I don't expect this move will have a noticeable impact on GPU performance.

The 13-inch MacBook Pro has absolutely no GPU options, all you get is the on-die Intel HD Graphics 3000. Based on what we saw in our original mobile Sandy Bridge review this should mean that GPU performance between the two stays the same. Intel's HD Graphics 3000 is about the performance of a GeForce 320M, the latter is what was used in last year's 13-inch MBP.

Half Life 2: Episode 2 (Mac OS X)

For Starcraft II performance we brought over our two benchmarks from our PC CPU and GPU reviews. We don't have FRAPS availalble under OS X so we resort to measuring lowest instantaneous frame rate at a couple of points.

The two tests focus on different aspects of SC2 gameplay. The GPU test looks at general unit management performance, which tends to be less CPU bound and more GPU bound. The CPU test looks at performance during a very large battle which, as you might guess, is largely influenced by CPU performance. 

Starcraft II—AT GPU Bench (Mac OS X)

Starcraft II—AT CPU Bench (Mac OS X)

Under OS X, the new HD Graphics 3000 GPU is actually about the same performance or even faster than the 2010 13-inch's GeForce 320M. Remember that Apple does a lot of its own driver writing under OS X and the SNB GPU received some TLC from Apple in the form of very well optimized drivers.

World of Warcraft (Windows 7)

Left 4 Dead (Windows 7)

Under Windows running WoW the situation is quite different and I'm not entirely sure why. Either Apple is very aggressive with driver optimizations under OS X or there's some other funniness happening under Windows (more on this later).

I did notice some bouts of instability with the 13-inch MacBook Pro as well as minor graphical corruption on the screen. Early on whenever I'd boot the system up I'd get a copy of the mouse cursor in the upper left of the screen.

15-inch MacBook Pro GPU Performance

Next up is the 15-inch MBP gaming performance comparison.

For 15-inch users the Radeon HD 6490M is pretty much the same speed as last year's GeForce GT 330M (if not marginally faster). The Radeon HD 6750M however is a lot faster. In fact, the performance improvement and increase in frame buffer you get with the 6750M is well worth the upgrade. If you're buying a 15-inch MacBook Pro and plan on gaming or using a high-res external display, get the 6750M.

Half Life 2: Episode 2 (Mac OS X)

Half Life 2: Episode 2 (Mac OS X)

Half Life 2: Episode 2 (Mac OS X)

Starcraft II—AT GPU Bench (Mac OS X)

Starcraft II—AT GPU Bench (Mac OS X)

Starcraft II—AT CPU Bench (Mac OS X)

Starcraft II—AT CPU Bench (Mac OS X)

6Gbps Performance & SSD Recommendations The dGPU: Killing Battery Life
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  • IntelUser2000 - Friday, March 11, 2011 - link

    You don't know that, testing multiple systems over the years should have shown performance differences between manufacturers with identical hardware is minimal(<5%). Meaning its not Apple's fault. GPU bound doesn't mean rest of the systems woud have zero effect.

    It's not like the 2820QM is 50% faster, its 20-30% faster. The total of which could have been derived from:

    1. Quad core vs. Dual core
    2. HD3000 in the 2820QM has max clock of 1.3GHz, vs. 1.2GHz in the 2410M
    3. Clock speed of the 2820QM is quite higher in gaming scenarios
    4. LLC is shared between CPU and Graphics. 2410M has less than half the LLC of 2820QM
    5. Even at 20 fps, CPU has some impact, we're not talking 3-5 fps here

    It's quite reasonable to assume, in 3DMark03 and 05, which are explicitely single threaded, benefits from everything except #1, and frames should be high enough for CPU to affect it. Games with bigger gaps, quad core would explain to the difference, even as little as 5%.
    Reply
  • JarredWalton - Friday, March 11, 2011 - link

    I should have another dual-core SNB setup shortly, with HD 3000, so we'll be able to see how that does.

    Anyway, we're not really focusing on 3DMarks, because they're not games. Looking just at the games, there's a larger than expected gap in the performance. Remember: we've been largely GPU limited with something like the GeForce G 310M using Core i3-330UM ULV vs. Core i3-370. That's a doubling of clock speed on the CPU, and the result was: http://www.anandtech.com/bench/Product/236?vs=244 That's a 2 to 14% difference, with the exception of the heavily CPU dependent StarCraft II (which is 155% faster with the U35Jc).

    Or if you want a significantly faster GPU comparison (i.e. so the onus is on the CPU), look at the Alienware M11x R2 vs. the ASUS N82JV: http://www.anandtech.com/bench/Product/246?vs=257 Again, much faster GPU than the HD 3000 and we're only seeing 10 to 25% difference in performance for low detail gaming. At medium detail, the difference between the two platforms drops to just 0 to 15% (but it grows to 28% in BFBC2 for some reason).

    Compare that spread to the 15 to 33% difference between the i5-2415M and the i7-2820QM at low detail, and perhaps even more telling is the difference remains large at medium settings (16.7 to 44% for the i7-2820QM, except SC2 turns the tables and leads by 37%). The theoretical clock speed difference on the IGP is only 8.3%, and we're seeing two to four times that much -- the average is around 22% faster, give or take. StarCraft II is a prime example of the funkiness we're talking about: the 2820QM is 31% faster at low, but the 2415M is 37% faster at medium? That's not right....

    Whatever is going on, I can say this much: it's not just about the CPU performance potential. I'll wager than when I test the dual-core SNB Windows notebook (an ASUS model) that scores in gaming will be a lot closer than what the MBP13 managed. We'll see....
    Reply
  • IntelUser2000 - Saturday, March 19, 2011 - link

    I forgot one more thing. The quad core Sandy Bridge mobile chips support DDR3-1600 and dual core ones only up to DDR3-1333. Reply
  • mczak - Thursday, March 10, 2011 - link

    memory bus width of HD6490M and H6750M is listed as 128bit/256bit. That's quite wrong, should be 64bit/128bit.

    btw I'm wondering what's the impact on battery life for the HD6490M? It isn't THAT much faster than the HD3000, so I'm wondering if at least the power consumption isn't that much higher neither...
    Reply
  • Anand Lal Shimpi - Thursday, March 10, 2011 - link

    Thanks for the correction :)

    Take care,
    Anand
    Reply
  • gstrickler - Thursday, March 10, 2011 - link

    Anand, I would like to see heat and maximum power consumption of the 15" with the dGPU disabled using gfxCardStatus. For those of us who aren't gamers and don't need OpenCL, the dGPU is basically just a waste of power (and therefore, battery life) and a waste of money. Those should be fairly quick tests. Reply
  • Nickel020 - Thursday, March 10, 2011 - link

    The 2010 Macbooks with the Nvidia GPUs and Optimus switch to the iGPU again even if you don't close the application, right? Is this a general ATI issue that's also like this on Windows notebooks or is it only like this on OS X? This seems like quite an unnecessary hassle, actually having to manage it yourself. Not as bad as having to log off like on my late 2008 Macbook Pro, but still inconvenient. Reply
  • tipoo - Thursday, March 10, 2011 - link

    Huh? You don't have to manage it yourself. Reply
  • Nickel020 - Friday, March 11, 2011 - link

    Well if you don't want to use the dGPU when it's not necessary you kind of have to manage it yourself. If I don't want to have the dGPU power up while web browsing and make the Macbook hotter I have to manually switch to the iGPU with gfxCardStatus. I mean I can leave it set to iGPU, but then I will still manually have to switch to the dGPU when I need the dGPU. So I will have to manage it manually.

    I would really have liked to see more of a comparison with how the GPU switching works in the 2010 Macbook Pros. I mean I can look it up, but I can find most of the info in the review somewhere else too; the point of the review is kind of to have it all the info in one place, and not having to look stuff up.
    Reply
  • tajmahal42 - Friday, March 11, 2011 - link

    I think switching behaviour should be exactly the same for the 2010 and 2011 MacBook Pros, as the switching is done by the Mac OS, not by the Hardware.

    Apparently, Chrome doesn't properly close done Flash when it doesn't need it anymore or something, so the OS thinks it should still be using the dGPU.
    Reply

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