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TekSpek ArrowGPU - Graphics ArrowNVIDIA GeForce GTX 660
NVIDIA GeForce GTX 660

NVIDIA GeForce GTX 660
Date issued: 13/09/2012

A new breed of Kepler

NVIDIA has given its consumer graphics card range a complete makeover in 2012 with the launch of the GeForce GTX 680, GeForce GTX 670 and GeForce GTX 660 Ti.

The high-performance range, built from the award-winning Kepler GK104 die, has deservedly lapped up the plaudits, but the products thus far have demanded premium price tags of over £200 rising to as much as £400 for the fastest single-GPU solution, the GTX 680.

In an effort to bring the goodness of the Kepler architecture down to a more mainstream audience, NVIDIA is now introducing new silicon dubbed GK106, whose first retail interpretation takes the form of the all-new GeForce GTX 660.

Perusing the detailed specification chart below, we have the GeForce GTX 660 (GK106 die) shown on the far right. The three left-most GPUs are, you guessed it, the existing GK104 variants. Haphazardly interchanging retail and code-names, GK106 is based on a genuinely different piece of silicon than its GTX 600 brethren. Imbued with 2.54bn transistors on a 221mm²-sized die it is around 25 per cent smaller than GK104. This is good news for NVIDIA and you, the gamer, because it enables cheaper, power-efficient cards to be built.

GPU GeForce GTX 680
(2,048MB)
GeForce GTX 670
(2,048MB)
GeForce GTX 660 Ti
(2,048MB)
GeForce GTX 660
(2,048MB)
Die codename Kepler GK104 Kepler GK104 Kepler GK104 Kepler GK106
DX API 11.1 11.1 11.1 11.1
Process 28nm 28nm 28nm 28nm
Transistors 3.54bn 3.54bn 3.54bn 2.54bn
Die Size 294mm² 294mm² 294mm² 221mm²
SMX units 8 7 7 5
Processors 1,536 1,344 1,344 960
Texture Units 128 112 112 80
ROP Units 32 32 24 24
GPU Clock (MHz) 1,006 (1,058) 915 (980) 915 (980) 980 (1,033)
Shader Clock (MHz) 1,006 (1,058) 915 (980) 915 (980) 980 (1,033)
GFLOPS 3,090 2,459 2,459 1,882
Memory Clock (MHz) 6,008 6,008 6,008 6,008
Memory Bus (bits) 256 256 192 192
Max bandwidth (GB/s) 192.3 192.3 144.2 144.2
Power Connectors 6+6 6+6 6+6 6-pin
TDP (watts) 195 170 150 140
GFLOPS per watt 15.84 14.46 16.39 13.44

Understand, however, that while the underlying architecture between the two is practically the same, the GK106, which has a smaller die, has to lose out somewhere. That loss is encountered on what we call the 'top end' of the GPU, where the shaders, texture units and tessellation units are located. GK106 drops its SMX complement to five, from a possible eight, and consequently has 960 shaders and 80 texture units, compared with GTX 660 Ti's 1,344 and 112.

NVIDIA patently realises that such a chop is not going to play well if games require masses of shading and texturing. Ameliorating this shading/texturing shortfall somewhat, the GK106 is beefed up with a lofty 980MHz core, boosting to an average of 1,033MHz using Turbo Boost technology.

While the top section of the GPU is stunted in relation to its bigger brother, the back-end is, for all intents and purposes, a copy. 6Gbps memory interfaces with a 192-bit bus and produces, at full gas, 144.2GB/s of juicy bandwidth. 24 ROPs take care of image-quality work and 384KB of L2 cache keeps everything chugging along nicely.

Smaller die, lower power, right? NVIDIA assigns GK106 a 140W TDP but goes further and states average in-game power is likely to be around 115W. This should lead to retail cards with minimal cooling and, perhaps, even passively-cooled examples from some of the more adventurous add-in card partners. 140W, too, requires cards to be furnished with only a single six-pin auxiliary power connector.

Architected to perform well at high-quality settings at the ubiquitous 1,920x1,080 (1080p) resolution, the basic GeForce GTX 660 2GB cards will be made available for £179, rising to £200 for special-edition, overclocked designs. Casting an eye over to AMD's Radeons, this means NVIDIA's newest card has to do well against the rival Radeon HD 7850 and HD 7870.

Performance

As shown by benchmarks from leading online publications, a factory-overclocked GeForce GTX 660 will perform roughly 20 per cent slower than the bigger, more expensive GeForce GTX 660 Ti.

Interesting to note, however, that the new GK106-based card performs better than the previous-generation champ - GeForce GTX 580 - and comes out ahead of both Radeon HD 7870 and HD 7850 in the widely-used 3DMark 11 benchmark.

Summary

By making available roughly 80 per cent of the performance of the GeForce GTX 660 Ti in a smaller, more efficient and more affordable package, NVIDIA has introduced a sub-£200 card with plenty of mainstream appeal.

With built-in Turbo Boost and all of Kepler's award-winning features - including 3D Vision support and the ability to run four displays from a single card - the GeForce GTX 660 is an excellent fit for full-HD gaming and more.

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