GT 650M GDDR5 vs DDR3 and 2GB vs 1GB memory capacity

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I really don’t know why so many times stores and menufacturers hide such data from the buyer but it’s annoying. This time, we’ll do a little comparison of two versions of the popular GT 650M GPU – the DDR3 and the GDDR5 version. Many GPUs from AMD and Nvidia (and Intel too, in their integrated HD graphics chip) come in two or more variations. Many time you’ll see these two variations: lower core clock with higher memory bandwidth and higher core clock coupled with a lower memory bandwidth with the latter being the faster one usually. Examples are the GT 650M and the Radeon 7670M  / 7690M and more. In both cases, the GDDR5 version is the faster one, but it’s not always the case.

Not every GPU needs high memory bandwidth. GDDR5 probably wouldn’t matter for a GT 620M GDDR5 or even GT 630M (they are not offered either) – they just won’t be able to use that bandwidth anyway, but in the case of the GT 650M level cards it sometimes matters considerably and why only sometimes? because it depends on the application / game that uses the card and the games’ settings – low resolutions scenarious usually less prone to low memory bandwidth problems.

 

The following table contains results from three systems with GT 650M:

1. I7-3610QM (2.3GHZ-3.3GHZ) and GT 650M 1GB GDDR5 GPU.

2. I7-3720QM (2.6GHZ-3.6GHz) and GT 650M 2GB GDDR5 GPU.

3. I7-3720QM (2.6GHZ-3.6GHz) and GT 650M 2GB DDR3 GPU.

 

The point of this test is to show cases where 2GB has an advantage over 1GB GT 650M and when GDDR5 has an advantage over DDR3. Now, disclaimer – the tests were done with different drivers sometimes, a thing that can have a significant impact on the results. However, I tried to make it as consistent as I could, taking only results that are consistent over several machines and tests.

Settings GT 650M 1GB GDDR5,I7-3610QM (FPS) GT 650M 2GB GDDR5,I7-3720QM (FPS) GT 650M 2GB DDR3,I7-3720QM (FPS)
Mass Effect 1920×1080, all on, onAA 8xAF ~46 ~49 ~35
Diablo 3 1920×1080, high, on AA ~44 ~41
Skyrim 1920×1080 Ultra Preset 8xAA 16xAF ~24 ~25
Anno 2070 1920×1080 very high onAA 4xAF ~36 ~36 ~37
Battlefield 3 1366×768 high -AA 16xAF ~30 ~34 ~31
CoD: Modern Warfare 3 1920×1080 Extra, all on, Image Quality: Native 4xAA -AF ~36 ~44
Dirt 3 1920×1080 Ultra Preset 4xAA -AF  ~26 ~26 ~26 : (core on 950MHZ with Turbo GPU)
1366×768 High Preset 2xAA -AF ~84 ~85 ~77 : (core on 950MHZ with Turbo GPU)

You can see the full results here. You can see that in many cases the GDDR5 has an a small advantage, but it usually fits the difference in CPU clocks as the 3720QM is clocked 300MHZ higher than the 3610QM (+13%). In some other cases – like Dirt 3 – the GDDR5 has a clear advantage over the DDR3 version despite the fact the it has considerably higher core clock. In 1366×768 resolution, the GDDR5 has a nice ~10% gain over the DDR3 version no matter how much memory and even though the DDR3 system has the faster 3720QM cpu. However, when going up to 1080p resolution and highest settings + 4xAA the results flattens which means that either the cpu is a bottleneck in these settings or the GPU is the bottleneck. Since we see no difference between 3610QM system and the 3720QM we suspect that the GPU is the bottleneck in that case and the additional 1GB doesn’t help. With Mass Effect 3 we see the same difference between the GDDR5 and DDR3 version.

Another intersting case is the CoD: Modern Warfare 3 game. On highest settings, the 2GB GT 650M / I7-3720QM system has a good 22% gain over the GDDR5 1GB version. This cannot be explained by the difference in cpu core clock itself and means that probably the CoD loves the additional 1GB memory.

 

More evidences are in the desktop part GT 640M (1, 2) – The GT 640M, with higher transistor count, same shaders count, higher clocks and newer architecture comes behind the GTS 450 – why? probably because the GTS 450 is equipped with the GDDR5 memory.

The GT 640M is the same as the same as the mobile parts GT 650M / GTX 660M only with higher default clocks and with a DDR3 memory.

 

So, GDDR5 or DDR3?

Well, most of the systems comes with the GDDR5 version, but if the one you one doesn’t, you better check for possible upgrade. As a rule of thumb, you better take the GDDR5 version, but it really depends on the price. If it’s in the range of 50$ take or give, then it’s probably a good deal as you won’t find currently a faster GPU even with the added premium, but unless the upgrade includes another 1GB then I wouldn’t spend more than 100$ on it.

 

And 2GB vs 1GB?

Again, depends on the price and your needs. Generally – yes, there is a reason for it, but you should consider two things:

1. Are you going to use it with 1080p resolutions or lower? – for 1366×768 resolution I wouldn’t bother. For 1600×900 resolutions and especially 1080p and up I say yes. If it’s like 50$ then go for it.

2. Are you playing games that will use it? – check the games list on sites that tested the GT 650M 2GB to understand if it helps in the specific game(s) you want to play.

 

The bottom line is that you should define your needs and act according to them. I would automatically buy the 2GB GDDR5 version with fastest cpu because the price might be in the range of better GPUs system which will be faster in gaming scenarious and it’s true not only in the GT 650M case. Moreover, you might decide that the added price is just too much and you better buy flowers to your loved ones instead.

 

Here are some GT 650M deals