Review Index:

Nvidia GeForce GT 640M Review: Kepler Arrives For Mobile

Author: Matt Smith
Subject: Mobile
Manufacturer: Nvidia

Performance, Verdict

 Synthetic Benchmarks

We always begin our look at GPU performance with the synthetic benchmarks, 3DMark 06 and 3DMark 11. Let’s dive right in to the former.

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Here we see that 3DMark 06 provides a score that is well below the GT 555M, but much higher than the Radeon 6720G2. This result is decent, but far from excellent. 

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3DMark 11 is a different story. The score of 1785 betters the GT 555M (that has 144 CUDA cores and runs at a frequency of 753 MHz) by no small margin and also defeats the Radeon HD 6720G2 solution found in the ASUS K53T by a couple hundred points. The score provided by the Radeon HD 6990M shows that the GT 640M is still well within the range of what I consider a mid-range component, but it does appear that Nvidia’s new architecture is much quicker than the out-going components and faster than the competition from AMD.

Game Benchmarks

In this section we are going to look at our standard gaming test suite. Though we usually test “just” three games, they are specifically selected to provide examples of a wide range of games on the market, from those that place little demand on the GPU to those that are extremely difficult to run smoothly on laptop hardware. As usual, we start with our least demanding title - Dawn Of War 2: Retribution.

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Here we see that the game is more than playable, but doesn’t run as quickly than you’d imagine. In fact, the performance isn’t much better than some Intel HD 3000 laptops.

Why is this? While this Acer may have a mid-range GPU, it still has a ultrabook processor. Our testing has consistantly shown that Dawn of War 2: Retribution is particularly sensitive to processor performance.

Let’s move on to something more GPU reliant, such as Just Cause 2.

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That’s more like it. In this game we see that the GT 640M, even when paired with a low-voltage processor, is able to nearly beat the GT 555M in the Alienware M14x. That's a huge performance improvement over the last generation. 

Now let’s look at a game Nvidia referenced constantly during its Kepler unveil - Battlefield 3. This is among the most demanding games on the market today and even entry-level gaming laptops struggle to run it well. How will the GT 640M fair?

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How’s that for generational improvement? The new Kepler GT 640M defeats the previous GT 555M in the Alienware M14x by a small but noticeable margin. It also creams the Radeon APU/GPU combination found in the ASUS K53T. It would appear that the new GT 640M is a very capable part even when paired with a low-voltage CPU.

Is It Playable?

As mentioned, Nvidia claims that DirectX 11 titles from 2011 are playable on the GT 640M at a resolution of 1366x768 with high detail presets. When making this claim they specifically sited some popular titles including Batman: Arkham City, Battlefield 3, Deux Es: Human Revolution and Skyrim.

So, are these claims accurate? Let’s find out by looking at a min/max/average from these games. This is real gameplay recorded via FRAPS. For simplicity’s sake, we recorded gameplay from early levels of each game (besides Skyrim, which has no “levels” per say – we recorded gameplay from Whiterun instead).

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It looks like Nvidia has delivered on its promise. These games all ran at over 30 FPS – and both Skyrim and Deus Ex ran at over 40 FPS. This may be a mid-range part, but it is fully capable of running today’s most demanding titles.


One of the tactics used by Nvidia to squeeze maximum performance out of the new Kepler mobile chips is performance scaling. Every laptop has a maximum amount of heat it can cool - so why not make sure all of it is being used?

The answer to that question starts to become evident when playing games on this laptop. While the palmrest remains in the mid-80s, the middle of the keyboard becomes extremely warm, reaching temperatures up to 105 degrees.

That’s nothing compared to center-bottom of the laptop, where we read temperatures of up to 128 degrees after playing Battlefield 3 on Ultra. That’s unacceptably warm - it’s hard to imagine using this laptop on anything besides a desk if you want to engage the GPU. 

I asked an Nvidia rep what they were going to do to ensure that the dynamic performance scaling did not result in high external temperatures. The answer I received was that it’s up to the laptop manufacturer as the thermal capacity of the chassis is often determined before they select a GPU. It appears Acer has been very liberal with the maximum temperatures it will tolerate. 


The performance gain between this generation and the last is substantial. Overall, the GT 640 appears to offer performance on par with the old GT 555M. This should have the effect of lowering the money you have to spend to buy a laptop with acceptable 3D performance. Our Acer Aspire review unit has an MSRP of $799, which is quite a bit less than systems available with the GT 555M.

Intel HD 4000 graphics will, of course, change the balance of this equation somewhat. Thanks to the leaks from Anandtech we already have a decent idea of what that part will provide, and it’s not bad. But it seems Nvidia will be able to offer value beyond integrated graphics.

The company also has stated out that game compatibility is much better with its GPUs, and that’s a fair point. In reviewing Intel HD 3000 systems we have sometimes ran in to odd behavior in games, or games that would not launch at all.

Optimus is still a key feature with the Kepler series of mobility GPUs and it will allow OEMs to build ultrathin and light notebooks with discrete graphics - as we have here with this Acer model.  Battery life, while not gaming, should still be decided by the processor and platform regardless of the discrete GPU in use.  Power consumption with the GT 640M active is still something we want to test in our full review.

Our only concern is heat. It’s hard to know if the high temperatures put off by this laptop are representative of others, but if it is, heat could be the Achilles heel of this new GPU. Nvidia was eager to show that they could offer such great performance in a thin chassis, but perhaps they would have been better served by leading off with a more conventional laptop.

Still, heat isn’t enough to spoil the party, particularly since it didn’t result in any performance or stability issues. We suspect that Nvidia’s new Kepler based mobile GPUs will dominate the market. 

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March 13, 2012 | 09:38 PM - Posted by Anonymous (not verified)

When does the NDA lift?

March 13, 2012 | 10:05 PM - Posted by Brian (not verified)

Way to go trolling the internet: "Kepler preview tonight".

No one gives a shit about mobile. Give us GK104.

March 13, 2012 | 10:10 PM - Posted by Ryan Shrout

Hey, I said mobile Kepler in my post!

March 13, 2012 | 10:11 PM - Posted by Eggrenade

"...they so far are less capable of displaying rich 3D graphics than your typical smartphone or table."


March 13, 2012 | 10:48 PM - Posted by Ryan Shrout

We have some fancy technologically advanced tables here at PCPer.



March 13, 2012 | 10:16 PM - Posted by Rahul (not verified)

Can you give more information about the memory interface? Was it 64-bit, 128-bit etc and what is the net available bandwidth? Is there any "driver info" dialog or something similar and if so, can we get a screenshot? Not familiar with nvidia's interfaces, but AMD Catalyst has a "hardware info" dialog.

March 13, 2012 | 10:35 PM - Posted by Matt Smith

According to GPU-Z the bus width is 128 bit with a total bandwidth of 28.8 GB/s.

March 13, 2012 | 10:17 PM - Posted by Rahul (not verified)

Also thanks for providing this review. Pretty intriguing :)

March 13, 2012 | 11:51 PM - Posted by Anonymous (not verified)

Ryan, are you sure you have the right information for the 555M?

The version of the 555M that has a GPU clock of 753 MHz only has 96 CUDA cores, and the version that has 144 CUDA cores has a GPU clock of 590 MHz. As far as I know, there's not a version that has 144 CUDA cores and a 753 MHz clock.

Also, Alienware's website lists the card as having DDR3 memory, which is found on the 144 CUDA Core 590 MHz version of the 555M. The other version uses GDDR5 so it seems likely that the GPU clock is not 753 MHz.

March 14, 2012 | 09:15 AM - Posted by Ryan Shrout

Just going of the "up to" specs.

March 14, 2012 | 01:04 AM - Posted by zarga (not verified)

So basically it performs around 20% better than the ATI 6750M, thats a nice figure if the power consumption is low.

Anyway, how does that Acer qualify as an Ultrabook?? There are plenty of 15" laptops out there with the similar weight/size characteristics, fast CPU and bigger battery at the same time. For an Ultrabook, the Acer is too heavy, for being a proper workstation laptop its clearly underpowered.

March 14, 2012 | 06:50 AM - Posted by Anonymous (not verified)

Fix this nonsense:
"The GPU clock is 625 MHz , the Memory clock is 900 MHz and the Shader clock is 1250 MHz."

March 14, 2012 | 09:16 AM - Posted by Ryan Shrout

What is the "nonsense" here?

March 14, 2012 | 04:22 PM - Posted by Anonymous (not verified)

shader clock is.
no hotclock for kepler

March 14, 2012 | 07:52 PM - Posted by Ryan Shrout

You think...?


March 14, 2012 | 11:43 AM - Posted by Anonymous (not verified)

Are those temps fahrenheit or celsius?

March 14, 2012 | 10:25 PM - Posted by Matt Smith

Fahrenheit! If it was Celsius I'd stop playing games and start using the laptop as a hotplate.

March 14, 2012 | 02:26 PM - Posted by Anonymous (not verified)

So Kepler does have Shader hot clocks?

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March 14, 2012 | 04:32 PM - Posted by Anonymous (not verified)

can you tell something about the fixed function units?
the GT 540m had something around 4 ROPs and 16 TMUs I think, the 555m 1.5GB 24/32, what about the 640m?

March 20, 2012 | 03:07 PM - Posted by Anonymous (not verified)

I just want the mobile version of keplar to come out so i can have a decent gamming laptop for college >.>

December 14, 2012 | 03:49 PM - Posted by Anonymous (not verified)

Hi, i have this graphic card on another laptop, and it reaches 84 Celcius when playing a game like far cry 3, is this too hot for this graphic card or can it take the heat?

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