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Nvidia's GeForce GTX 760 graphics card reviewed


...and the GeForce GTX 770, too
— 8:00 AM on June 25, 2013

The GTX 700 series sure is growing fast. Over the past month alone, we've seen the arrival of the GeForce GTX 780, the GeForce GTX 770, and now, the GeForce GTX 760. We hardware reviewers have been working tirelessly to keep up, spending long days, nights, and weekends benchmarking the new arrivals.

When will it end?

Today, actually. Nvidia says it doesn't plan to bring the GTX 700 series down further beyond the GTX 760. The company's desktop graphics lineup will to remain as it is through the fall. Phew!

Oh, don't get us wrong. We love to see fresh meat in the GPU market. However, the GTX 700 series isn't based on new silicon. In each case, Nvidia has simply taken an old GPU and turned a few knobs, moved a few dials, and flipped a few switches to keep it from getting stale. All that tweaking has yielded some decidedly welcome performance-per-dollar improvements, but next-gen parts these are not.

The GeForce GTX 760 continues this succession of value-conscious makeovers by replacing the old GeForce GTX 660 Ti at a slightly reduced price: $249. As you're about to see, Nvidia has made some interesting changes to the way it hobbles the GK104 chip to make this thing. Some unit counts have been increased, others have been reduced, and clock speeds have gone up. The result is a card that may be slower in some tasks but could be a better performer in today's games—all for less money than its predecessor. That's perhaps not as swoon-worthy as a brand-new graphics architecture, but it's definitely something.

The GeForce GTX 760
The star of this morning's show hails from the depths of Nvidia's secret underground bunker. Or, more likely, some kind of QA lab or something.

Give us a twirl, won't you, sweetheart?

From the outside, the GeForce GTX 760 looks pretty much exactly like its older sister, the GeForce GTX 660 Ti. The stock cooler is the same. The circuit board is just as stubby, and there are still two 6-pin PCI Express connectors providing power to the card.

What's going on under the hood is quite different, though. With the GTX 660 Ti, Nvidia lopped off one of the GK104 chip's eight shader multiprocessors (SMXes), leaving 1344 shader ALUs and 110 texels per clock of texture filtering power. The company also disabled one of the four ROP partitions and one of the four memory controllers, which gave us, respectively, 24 pixels per clock of resolve power and a 192-bit path to memory.

GPU
base
clock
(MHz)
GPU
boost
clock
(MHz)
Shader
ALUs
Textures
filtered/
clock
ROP
pixels/
clock
Memory
transfer
rate
Memory
interface
width
(bits)
Peak
power
draw
GeForce GTX 660 Ti 915 980 1344 112 24 6 GT/s 192 150W
GeForce GTX 680 1006 1058 1536 128 32 6 GT/s 256 195W
GeForce GTX 760 980 1033 1152 96 32 6 GT/s 256 170W
GeForce GTX 770 1046 1085 1536 128 32 7 GT/s 256 230W
GeForce GTX 780 863 900 2304 192 48 6 GT/s 384 250W

In the GeForce GTX 760, all of the ROP partitions are enabled, as are all of the memory controllers. That means we have 32 pixels per clock and a full-fat 256-bit memory interface. However, one additional shader multiprocessor has been culled, which means we're down to 1152 ALUs and 96 textures per clock.

The way Nvidia disables the SMXes also means different GTX 760 cards will have different tessellation capabilities. Remember, the GK104 chip's eight SMX units are paired up inside four GPCs, or graphics processing clusters, and each GPC has a raster engine that can rasterize one triangle per clock. To make a GTX 760, Nvidia can either disable one entire GPC or turn off two SMXes in two separate GPCs. In the former configuration, one of the raster engines goes dark, and the card rasterizes three triangles per clock. In the latter, all raster engines survive the culling, and the raster rate goes up to four per clock.

This isn't the first time Nvidia has played musical chairs with raster engines. The GeForce GTX 780 is similarly inconsistent, with either four or five triangles rasterized per clock depending on how the GK110 chip is pared down. Offering inconsistent specs in a single product may not be ideal, but the ability to prune any two SMXes (or any three in the GTX 780) gives Nvidia much more flexibility to repurpose defective GPUs. Also, as far as the GTX 760 is concerned, even the worst-case scenario beats the competition, since AMD's Radeon HD 7950 Boost only rasterizes two triangles per clock.

Speaking of clocks, the the GeForce GTX 760 also boasts a higher clock speed than the GTX 660 Ti. Nvidia has cranked up the base speed from 915MHz to 980MHz, and it's pumped up the peak Boost speed from 980MHz to 1033MHz. Part of the gain comes courtesy of Nvidia's GPU Boost 2.0 algorithm, which uses GPU temperatures, not power draw, as the main factor to determine maximum speeds. When temperatures are low enough, GPU Boost 2.0 can raise voltages to increase the amount of clock-speed headroom for a given chip. No doubt thanks to that algorithm, you can expect to see even higher-clocked versions of the GTX 760 from Nvidia's partners. Both Gigabyte and MSI will have cards with 1085MHz base clocks and 1150MHz Boost clocks, and some vendors will offer even faster models.

  Peak pixel
fill rate
(Gpixels/s)
Peak
bilinear
filtering
(Gtexels/s)
Peak
bilinear
fp16
filtering
(Gtexels/s)
Peak
shader
arithmetic
rate
(tflops)
Peak
rasterization
rate
(Gtris/s)
Memory
bandwidth
(GB/s)
GeForce GTX 660 Ti 24 110 110 2.6 3.9 144
GeForce GTX 680 34 135 135 3.3 4.2 192
GeForce GTX 760 33 99 99 2.4 3.1 or 4.1 192
GeForce GTX 770 35 139 139 3.3 4.3 224
GeForce GTX 780 43 173 173 4.2 3.6 or 4.5 288
Radeon HD 7870 GHz 32 80 40 2.6 2.0 154
Radeon HD 7950 Boost 30 104 52 3.3 1.9 240
Radeon HD 7970 GHz 34 134 67 4.3 2.1 288

Here's how the GTX 760's combination of higher speeds and tweaked unit counts translates into peak theoretical rates. As you can see, the higher clocks don't quite make up for the missing SMX—peak texture filtering and peak shader performance are both lower than on the GTX 660 Ti. At the same time, the peak pixel fill rate has gone up a fair bit, which should mean better antialiasing resolve performance. Memory bandwidth has increased substantially, as well.

Compared to the Radeon HD 7950 Boost, the GTX 760 looks superior or competitive in all but raw shader speed and memory bandwidth. Of course, the 7950 Boost also has a wider, 384-bit memory interface, and it's a slightly more expensive card right now. (Prices start at $279.99, or $259.99 after a mail-in rebate.)

Source: Nvidia

At 170W, the GeForce GTX 760's power envelope is a little larger than the GeForce GTX 660 Ti's 150W TDP. To keep noise levels in check, Nvidia has implemented a revised fan control algorithm that curbs fluctuations in speed. The result should be a more consistent noise profile—one that's hopefully easier to tune out. A similar algorithm debuted in the GTX 780 last month, and it seemed to work wonders. Of course, the GTX 760 has a different heatsink and fan design, so we'll have to do some hands-on noise testing to see how it fares.

But before that, let's first have a look at another member of the GTX 700 series.