GeForce GT 640 DDR3 vs GeForce GTX 650 Ti 2GB

Intro

Compare those specifications to the GeForce GTX 650 Ti 2GB, which features core clock speeds of 928 MHz on the GPU, and 1350 MHz on the 2048 MB of GDDR5 RAM. It features 768 SPUs along with 64 TAUs and 16 Rasterization Operator Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce GT 640 DDR3		65 Watts
GeForce GTX 650 Ti 2GB		110 Watts
	Difference: 45 Watts (69%)

Memory Bandwidth

Theoretically, the GeForce GTX 650 Ti 2GB should perform much faster than the GeForce GT 640 DDR3 overall. (explain)

GeForce GTX 650 Ti 2GB		86400 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 29376 (52%)

Texel Rate

The GeForce GTX 650 Ti 2GB should be much (more or less 106%) faster with regards to texture filtering than the GeForce GT 640 DDR3. (explain)

GeForce GTX 650 Ti 2GB		59392 Mtexels/sec
GeForce GT 640 DDR3		28800 Mtexels/sec
	Difference: 30592 (106%)

Pixel Rate

If running with lots of anti-aliasing is important to you, then the GeForce GTX 650 Ti 2GB is a better choice, though not by far. (explain)

GeForce GTX 650 Ti 2GB		14848 Mpixels/sec
GeForce GT 640 DDR3		14400 Mpixels/sec
	Difference: 448 (3%)

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: Memory bandwidth is the maximum amount of data (measured in MB per second) that can be transferred past the external memory interface in one second. It is worked out by multiplying the card's bus width by its memory speed. In the case of DDR memory, the result should be multiplied by 2 once again. If it uses DDR5, multiply by ANOTHER 2x. The better the card's memory bandwidth, the faster the card will be in general. It especially helps with AA, High Dynamic Range and higher screen resolutions.

Texel Rate: Texel rate is the maximum number of texture map elements (texels) that are processed per second. This figure is worked out by multiplying the total number of texture units of the card by the core clock speed of the chip. The better this number, the better the video card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels in a second.

Pixel Rate: Pixel rate is the maximum amount of pixels that the graphics card could possibly record to the local memory per second - measured in millions of pixels per second. The figure is worked out by multiplying the number of ROPs by the the core speed of the card. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel output rate is also dependant on many other factors, most notably the memory bandwidth - the lower the memory bandwidth is, the lower the potential to get to the maximum fill rate.