NVIDIA GTX 660 2GB Review

Author: SKYMTL
Date: September 12, 2012
Product Name: GTX 660 2GB
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In today’s gaming market, there’s a very simple rule of thumb: everyone loves reading about high end graphics cards, but with affordability dictating purchase decisions, most gamers will forego expensive flagship products. The $399 to $299 segments take up most of the slack but the sub-$250 market is where AMD and NVIDIA typically hit their price / performance stride. Looking back at previous and current generations, this is where the ultra popular 8800 GT, GTX 460, HD 6870 and HD 7850 cut their teeth before inevitable price drops brought them to even lower price points.

NVIDAI calls this narrow yet popular slice of the overall GPU pie the “gamers’ sweet spot” but up until this point, they have been more than content to let the GTX 560 Ti and its ilk compete against the Pitcairn-based HD 7800-series. The battle has been somewhat lopsided but the entry of the new GeForce GTX 660 2GB is meant to effectively turn things around by utilizing an efficient GK106 core and setting a new benchmark in high performance affordability with a price of just $229.

NVIDIA’s GTX 660 Ti used a scaled down version of the GK104, a core which was used to great effect within two other high end cards: the GTX 670 and GTX 680. Since only so much can be cut from a given microarchitecture before it becomes inefficient and cost prohibitive for lower spec’d SKUs, another route was taken for the GTX 660. Even though it carries the same name as its larger sibling, the GTX 660 2GB uses a new core code-named GK106.

While it may still use the Kepler architecture championed by NVIDIA this generation, the GK106’s core layout is slightly different and more streamlined than the GK104’s 3.54 billion transistor payload. In its current form, the GK106 uses five SMX blocks, each with 192 CUDA cores and 16 Texture Units, resulting in a die with 960 CUDA cores and 80 TMUs. Four of these Streaming Multiprocessor blocks are paired up into separate Graphics Compute Clusters (with their associated Raster Engines) which leaves one lonely SMX for the final GPC. Naturally, this somewhat unbalanced approach has us wondering if the GK106 has a single 192-core SMX cut out in order to ensure the necessary performance segmentation between the GTX 660 Ti and GTX 660.

Aside from the typical core rendering functionalities, the GK106 also incorporates the usual 1:1:128 ratio for ROP, GDDR5 memory controller and L2 cache partitions. As such, it uses three partitions of eight ROPS (for a total of 24), three 128-bit memory controllers and 384KB of L2 cache. With a 192-bit memory interface, the mixed memory sizes from past generations have been incorporated here as well, allowing GK106-based cards to use 1.5GB, 2GB or 3GB of memory. In its reference form, the GTX 660 will utilize a 2GB framebuffer but expect the board partners to introduce custom 3GB cards in short order.

All of the changes wrapped into this core have resulted in a substantial die size savings which in effect lowers per unit costs and should hopefully improve yields as well. At 2.54 billion transistors, the GK106 is about 28% smaller than the GK104.

In terms of specifications, the GTX 660 is a combination of freshness coupled with a few instances of déjà vu. Its 960 cores, 24 ROPs and 80 TMUs are far enough removed from the Ti’s offerings that there should be little to no performance overlap, even with pre-overclocked cards from NVIDIA’s board partners. Meanwhile, the GK106’s low transistor count allows the GTX 660 to run at a blistering 980MHz –or 1033MHz and higher with Boost- without guzzling down too much power. As a matter of fact, even though its TDP is listed as 140W, the card shouldn’t consume more than 117W in typical gaming scenarios. This frugality may not seem like a big deal but it allows the GTX 660 to become a simple drop-in upgrade for users with older systems and slightly outdated power supplies.

The memory layout of this card hasn’t changed one iota from the GTX 660 Ti. Like its $299 sibling the GTX 660 uses 2GB of GDDR5 operating at 6Gbps on a 192 bit bus which is good for 144GB/s. This puts it within spitting distance of the 153.3GB/s offered by the HD 7870 and HD 7850 so expect very close performance in most bandwidth limited situations.

At $229, the GTX 660 slides neatly into NVIDIA current lineup between the GTX 660 Ti and the newly introduced GTX 650. For those of you wondering, the $109 GTX 650 is essentially a clone of the OEM-only GT 640 GDDR5 with higher clock speeds but the same GK107 core. We’ll be covering this card in depth soon but for the time being, it is a simple footnote next to the GTX 660 launch.

Within today’s market, NVIDIA didn’t really need all that much crystal ball gazing to determine where the GTX 660 2GB should end up. Currently they have AMD’s HD 7950 and virtually non-existent HD 7950 Boost Edition covered with the GTX 660 Ti. However, the $259 HD 7870 GHz Edition and $199 to $209 HD 7850 2GB have been wreaking havoc upon the mid range since their release more than half a year ago. Their judicious price cuts have brought pressure upon NVIDIA but that hasn’t stopped the GTX 660 from sliding neatly into a space between these two AMD competitors.

In essence, this new card has been parachuted into a minefield of strong products in the hope that it will offer a balance between two extremely popular alternative solutions. It’s also got some big shoes to fill since the GTX 560 Ti and GTX 460 were both considered leaders of their respective generations.

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