GTX 660M vs GT 650M GDDR5 – isn’t it the same?

(GTX 660M dealsGT 650M deals and best deals)


I suggest that you read the GT 650M GDDR5 vs GT 650M DDR3 revised article – it reveals more details about the GTX 660M and GT 650M GDDR5 and DDR3 models.



So, Kepler is out and brings some interesting cards to the mobile gaming world. The GT 650M and GTX 660M are two of the most interesting cards from the Kepler series. Unlike the GTX 670M and GTX 675M, the GTX 660M are real Kepler core based cards. The GT 660M offers almost the same power as the previous generation GTX 570M and not much less performance from the GTX 670M (See here GTX 660M vs GTX 670M performance article). The GT 650M is based on the same chip actually and have two version currently, the GDDR5@1000MHZ version and the DDR3@900MHZ version. Ofcouse, card makers can decide to set other clocks to their cards.


Lets take a look in this GT 650M and GT 660M simple table:

Model Core, shaders (vertex / geometry / pixel) memory and bandwidth Core speed
GTX 660M GDDR5 Kepler (GK107), 384 unified : 32 : 16, 28nm process GDDR5@1000MHZ-1250MHZ,  64GB/s 835MHZ
GT 650M GDDR5 Kepler (GK107), 384 unified : 32 : 16, 28nm process GDDR5@1000MHZ, 64GB/s 735MHZ
GT 650M DDR3 Kepler (GK107), 384 unified : 32 : 16, 28nm process DDR3@900MHZ, 28.8GB/s 850MHZ


As you can see, talking about dry data, the GTX 660M is actually the same as the GT 650M GDDR5 with higher core clocks. Nvidia’s Turbo mode reported to be working (see some of the games benchmark here) and allows up to 15% increase in speed depending on the sensed temperatures and power consumptions – GT 650M DDR3 GPUs cores were overclocked to 950MHZ. However, this is depends also on the maker of the laptop to decide if she wants to incorporate this feature into the bios. Now, the thing is you can theoretically overclock your GT 650M GDDR5 to the levels of the GT660M core clock. People around the web say you can also OC the GDDR5 from 2000MHZ to 2600MHZ (effective) (1). I wonder, and wished I could check it myself, if the GTX 660M can be OC’ed to the level of the GTX 670M – being an 28nm GPU, its TDP won’t be higher than the GTX 670M while offering the same performance.

What is the difference in practice, you ask? – Well, with the GTX 660M you know that you won’t have issues, probably. It is a designated solution for the stated speed and TDP and you know you’ll get it and supposedly will appear in laptops that can handle the additional 100MHZ and additionally, you get 2GB dedicated GPU memory with the GTX 660M while the GT 650M have also a 1GB version which you usually get (but usually upgradable too). However, it’s only 100MHZ difference which is a joke, so I wouldn’t get to worried if I were to OC the GT 650M. Keep in mind that there is a considerable variation in the cores that get out of Nvidia’s oven. Some cores will be hotter and some less, some will have higher OC capabilities and some less and you should note that with a serious OC’ing, your GPU will probably exceed the stated TDP of 45W for the GT 650M.

Results from notebookcheck. I’ve filtered quirky results. Some of the numbers include the Nvidia Turbo which adds up to 15% to the core clock. Many of the the GT 650M are with 835MHZ (instead 735MHZ), like the GTX 660M, thanks to the Turbo.

Settings GTX 660M, I7-3610QM GT 650M GDDR5, I7-3610QM Difference
Mass Effect 3 1920×1080, all on, onAA 8xAF ~53 ~48 (735MHZ) +10%
Diablo 3 1920×1080, high, on AA ~68 ~60 +13%
Skyrim 1366×768 High Preset 8xAA 8xAF ~50 ~42 (745MHZ) +20%
Dirt Showdown 1366×768 high preset 2xAA, AF ~55 ~50 (745MHZ) +10%
BattleField 3 1366×768 high -AA 16xAF ~40 ~32 +25%
CoD: Modern Warfare 3 1920×1080 Extra, all on, native, 4xAF ~48 ~42 +15%
Max Payne 3 1366×768, Normal, DX10, AF and AA ~55 ~51 +7%
The Secret World 1366×768, High DX11, AF, AA ~36 ~36 (Turbo to 835MHZ) 0-13%

So you see that the theory true also in the numbers.

A word of warning – if you try to OC your card you should watch the temperatures of your system as you don’t want to keep your system on high degree even if it’s working because it unhealthy for the electronic staff.

About the numbers to back up the words. You can take a look in the GT 650M and GTX 660M pages on notebookcheck which include benchmarks in games for both GT 650M GDDR5 and DDR3 models and ofcourse, GT 660M benchmarks. You can see that the overall picture is that the performance difference between the GT 650M GDDR5 and the GTX 660M is very similar to the difference in their core speeds. Remember that the comparison is not perfect as the numbers do not come from the same test machine – different amount of memory in the GT 650M (1GB vs 2GB), different system hardware like chipset and cpu and different – and sometimes outdated – drivers in the test probably had affected the results.


Overclocking the GT 650M

The fellows from NBR forums made some instructions and posted some results of the OC attempts on the GT 650M. The results: the GT 650M GDDR5 is a little hell raiser! Some had success with OC’ing the core up to 1200-1250MHZ (from 835MHZ!) and the memory from 1000MHZ to ~1400MHZ!!

Although each chip is special in his own way, the GT 650M seems to be a very good overclocker. It should not have any problem with going up to the levels of the GTX 660M or close to that.

Concerning heat issues – some people say the overclocking had only a minor impact and besides, you better use a cooling pad to lower the temps anyway, even if you’re not going to OC your gpu.


Conclusions and decision: GT 650M GDDR5 or GTX 660M

My suggestion – I WOULDN’T take a GTX 660M laptop just for being equipped with a GTX 660M GPU. I would look for the overall quality – screen quality, build quality, heat and noise, battery runtime, looks if it matters and weigh it against the price difference. I’ll explain.

As we saw, the GK107 Kepler core in the heart of the GT 650M and GTX 660M should be highly overclockable. The GT 650M can achieve GTX 660M clocks and even higher and it seems pretty easy. It can achieve, therefore, the same performance as the GTX 660M but might exceed the 50W  TDP stated for the 660M. It also raises the thought that the GT 640M GDDR5 might as well be god enough for some decent OCing.

Now, as I figure it, the point with the GTX 660M besides the 100MHZ increase in speed, is that it comes usually with higher end and presumebly better machines overall concerning elements like build quality, heat and noise handling, screen quality, sound and more, but I guess there will be too much exceptions. Anyhow, take, for example, the Asus G55VW and the MSI GE60. The GE60 incorporates good FullHD display, the GT 650M 2GB GDDR5 GPU, 6GB DDR3 and good looks but the G55VW has a more metal body, very good heat and noise handling, also good quality FullHD display and GTX 660M GPU (review), but it costs good 300-400$ more and has no Optimus and low battery runtime. Does it worth it? good question – if you buy a laptop once in few years and you don’t need mobility then it would be good for because you know it has a better chance to survive (less heat, better body). Another example is the Lenovo Y580 can be found with a FullHD display and GTX 660M GPU for 1000$ and the HP dv6t-7000 with FullHD display is on sale for around 900-950$ with coupons in the last month, but still no reviews to tell how much good it really is.

We’ll wait for more reviews of new GT 650M and GTX 660M laptops and write some article about recommended laptops in this league. Meanwhile, I suggest the dv6t-7000 with coupons, the Sager NP6165 – both with GT 650M – to save money. It’s hard to recommend a laptop in this dynamic scene and it’s harder to recommend when there are few good reviews. So wait a bit if you can.