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GeForce GT 640 DDR3 vs GeForce GTS 450 1GB

Intro

The GeForce GT 640 DDR3 has core clock speeds of 900 MHz on the GPU, and 1782 MHz on the 2048 MB of DDR3 RAM. It features 384 SPUs as well as 32 Texture Address Units and 16 Rasterization Operator Units.

Compare those specifications to the GeForce GTS 450 1GB, which has core speeds of 783 MHz on the GPU, and 902 MHz on the 1024 MB of GDDR5 RAM. It features 192 SPUs as well as 32 Texture Address Units and 16 Rasterization Operator Units.

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce GT 640 DDR3		65 Watts
GeForce GTS 450 1GB		106 Watts
	Difference: 41 Watts (63%)

Memory Bandwidth

Performance-wise, the GeForce GTS 450 1GB should theoretically be just a bit superior to the GeForce GT 640 DDR3 in general. (explain)

GeForce GTS 450 1GB		57728 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 704 (1%)

Texel Rate

The GeForce GT 640 DDR3 is a little bit (approximately 15%) more effective at texture filtering than the GeForce GTS 450 1GB. (explain)

GeForce GT 640 DDR3		28800 Mtexels/sec
GeForce GTS 450 1GB		25056 Mtexels/sec
	Difference: 3744 (15%)

Pixel Rate

The GeForce GT 640 DDR3 will be just a bit (more or less 15%) faster with regards to anti-aliasing than the GeForce GTS 450 1GB, and should be capable of handling higher screen resolutions better. (explain)

GeForce GT 640 DDR3		14400 Mpixels/sec
GeForce GTS 450 1GB		12528 Mpixels/sec
	Difference: 1872 (15%)

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

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GeForce GT 640 DDR3

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GeForce GTS 450 1GB

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Specifications

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Model	GeForce GT 640 DDR3	GeForce GTS 450 1GB
Manufacturer	nVidia	nVidia
Year	June 2012	September 2010
Code Name	GK107	GF106
Memory	2048 MB	1024 MB
Core Speed	900 MHz	783 MHz
Memory Speed	3564 MHz	3608 MHz
Power (Max TDP)	65 watts	106 watts
Bandwidth	57024 MB/sec	57728 MB/sec
Texel Rate	28800 Mtexels/sec	25056 Mtexels/sec
Pixel Rate	14400 Mpixels/sec	12528 Mpixels/sec
Unified Shaders	384	192
Texture Mapping Units	32	32
Render Output Units	16	16
Bus Type	DDR3	GDDR5
Bus Width	128-bit	128-bit
Fab Process	28 nm	40 nm
Transistors	1300 million	1170 million
Bus	PCIe 3.0 x16	PCIe x16
DirectX Version	DirectX 11.0	DirectX 11
OpenGL Version	OpenGL 4.2	OpenGL 4.1

Memory Bandwidth: Memory bandwidth is the maximum amount of data (measured in megabytes per second) that can be moved over the external memory interface in one second. It is calculated by multiplying the bus width by the speed of its memory. If it uses DDR memory, it must be multiplied by 2 once again. If it uses DDR5, multiply by 4 instead. The higher the bandwidth is, the better 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 texture map elements (texels) that are applied per second. This number is worked out by multiplying the total texture units of the card by the core speed of the chip. The better the texel rate, the better the card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied per second.

Pixel Rate: Pixel rate is the maximum number of pixels the graphics card can possibly write to the local memory per second - measured in millions of pixels per second. The number is worked out by multiplying the amount of Raster Operations Pipelines by the the card's clock speed. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel rate also depends on many other factors, especially the memory bandwidth - the lower the memory bandwidth is, the lower the ability to get to the max fill rate.

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