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GeForce GT 640 DDR3 vs GeForce GTS 450 1GB

Intro

The GeForce GT 640 DDR3 comes with core 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 ROPs.

Compare all that to the GeForce GTS 450 1GB, which features GPU clock speed of 783 MHz, and 1024 MB of GDDR5 memory running at 902 MHz through a 128-bit bus. It also is made up of 192 Stream Processors, 32 Texture Address Units, and 16 ROPs.

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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

As far as performance goes, the GeForce GTS 450 1GB should theoretically be a bit superior to the GeForce GT 640 DDR3 overall. (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 (more or less 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 should be just a bit (approximately 15%) faster with regards to AA than the GeForce GTS 450 1GB, and also able to handle higher screen resolutions while still performing well. (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: Bandwidth is the max amount of data (measured in megabytes per second) that can be transported across the external memory interface in a second. The number is worked out by multiplying the card's interface width by the speed of its memory. In the case of DDR RAM, it must be multiplied by 2 again. If DDR5, multiply by ANOTHER 2x. The higher the card's memory bandwidth, 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 number of texture map elements (texels) that can be processed in one second. This number is worked out by multiplying the total amount of texture units of the card by the core speed of the chip. The higher this number, the better the card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels in one second.

Pixel Rate: Pixel rate is the maximum number of pixels that the graphics card could possibly write to the local memory per second - measured in millions of pixels per second. Pixel rate is calculated by multiplying the amount of Render Output Units by the clock speed of the card. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel output rate is also dependant on quite a few other factors, most notably the memory bandwidth of the card - the lower the bandwidth is, the lower the ability to reach the max fill rate.

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