GeForce GT 640 DDR3 vs GeForce GTX 660 Ti

Intro

Compare all of that to the GeForce GTX 660 Ti, which features a core clock speed of 915 MHz and a GDDR5 memory frequency of 1500 MHz. It also features a 192-bit bus, and makes use of a 28 nm design. It is made up of 1344 SPUs, 112 TAUs, and 24 ROPs.

Display Graphs

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Benchmarks

These are real-world performance benchmarks that were submitted by Hardware Compare users. The scores seen here are the average of all benchmarks submitted for each respective test and hardware.

3DMark Fire Strike Graphics Score

GeForce GTX 660 Ti		6013 points
GeForce GT 640 DDR3		1560 points
	Difference: 4453 (285%)

Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce GT 640 DDR3		65 Watts
GeForce GTX 660 Ti		150 Watts
	Difference: 85 Watts (131%)

Memory Bandwidth

Theoretically speaking, the GeForce GTX 660 Ti will be 153% quicker than the GeForce GT 640 DDR3 overall, due to its higher bandwidth. (explain)

GeForce GTX 660 Ti		144000 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 86976 (153%)

Texel Rate

The GeForce GTX 660 Ti should be quite a bit (more or less 256%) more effective at texture filtering than the GeForce GT 640 DDR3. (explain)

GeForce GTX 660 Ti		102480 Mtexels/sec
GeForce GT 640 DDR3		28800 Mtexels/sec
	Difference: 73680 (256%)

Pixel Rate

The GeForce GTX 660 Ti is a lot (approximately 53%) more effective at AA than the GeForce GT 640 DDR3, and also capable of handling higher resolutions more effectively. (explain)

GeForce GTX 660 Ti		21960 Mpixels/sec
GeForce GT 640 DDR3		14400 Mpixels/sec
	Difference: 7560 (53%)

Please note that the above 'benchmarks' are all just theoretical - the results were calculated based on the card's specifications, and real-world performance may (and probably will) vary at least a bit.

Price Comparison

Specifications

Memory Bandwidth: Bandwidth is the max amount of information (measured in MB per second) that can be moved past the external memory interface in one second. It's worked out by multiplying the interface width by its memory speed. In the case of DDR type memory, it should be multiplied by 2 once again. If DDR5, multiply by 4 instead. The better the card's memory bandwidth, the faster the card will be in general. It especially helps with anti-aliasing, HDR and higher screen resolutions.

Texel Rate: Texel rate is the maximum texture map elements (texels) that can be applied per second. This number is calculated by multiplying the total number of texture units of the card by the core clock speed of the chip. The better the texel rate, the better the graphics card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed per second.

Pixel Rate: Pixel rate is the maximum number of pixels the graphics card can possibly record to the local memory in one second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the number of colour ROPs by the the core clock speed. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel rate is also dependant on quite a few other factors, most notably the memory bandwidth - the lower the bandwidth is, the lower the potential to reach the maximum fill rate.