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GeForce GT 640 DDR3 vs Radeon HD 4830 512MB

Intro

The GeForce GT 640 DDR3 uses a 28 nm design. nVidia has clocked the core frequency at 900 MHz. The DDR3 RAM is set to run at a speed of 1782 MHz on this particular card. It features 384 SPUs as well as 32 Texture Address Units and 16 ROPs.

Compare all of that to the Radeon HD 4830 512MB, which comes with GPU clock speed of 575 MHz, and 512 MB of GDDR3 memory set to run at 900 MHz through a 256-bit bus. It also is comprised of 640(128x5) 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
Radeon HD 4830 512MB		95 Watts
	Difference: 30 Watts (46%)

Memory Bandwidth

Theoretically speaking, the Radeon HD 4830 512MB should be 1% quicker than the GeForce GT 640 DDR3 in general, because of its greater data rate. (explain)

Radeon HD 4830 512MB		57600 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 576 (1%)

Texel Rate

The GeForce GT 640 DDR3 should be a lot (more or less 57%) faster with regards to AF than the Radeon HD 4830 512MB. (explain)

GeForce GT 640 DDR3		28800 Mtexels/sec
Radeon HD 4830 512MB		18400 Mtexels/sec
	Difference: 10400 (57%)

Pixel Rate

If using lots of anti-aliasing is important to you, then the GeForce GT 640 DDR3 is a better choice, by far. (explain)

GeForce GT 640 DDR3		14400 Mpixels/sec
Radeon HD 4830 512MB		9200 Mpixels/sec
	Difference: 5200 (57%)

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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Radeon HD 4830 512MB

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Specifications

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Model	GeForce GT 640 DDR3	Radeon HD 4830 512MB
Manufacturer	nVidia	AMD
Year	June 2012	Oct 21, 2008
Code Name	GK107	RV770 LE
Memory	2048 MB	512 MB
Core Speed	900 MHz	575 MHz
Memory Speed	3564 MHz	1800 MHz
Power (Max TDP)	65 watts	95 watts
Bandwidth	57024 MB/sec	57600 MB/sec
Texel Rate	28800 Mtexels/sec	18400 Mtexels/sec
Pixel Rate	14400 Mpixels/sec	9200 Mpixels/sec
Unified Shaders	384	640(128x5)
Texture Mapping Units	32	32
Render Output Units	16	16
Bus Type	DDR3	GDDR3
Bus Width	128-bit	256-bit
Fab Process	28 nm	55 nm
Transistors	1300 million	956 million
Bus	PCIe 3.0 x16	PCIe 2.0 x16
DirectX Version	DirectX 11.0	DirectX 10.1
OpenGL Version	OpenGL 4.2	OpenGL 3.0

Memory Bandwidth: Memory bandwidth is the max amount of information (counted in MB per second) that can be moved across the external memory interface within a second. It's worked out by multiplying the card's interface width by the speed of its memory. In the case of DDR type RAM, it must be multiplied by 2 again. If DDR5, multiply by 4 instead. The higher the card's memory bandwidth, the faster the card will be in general. It especially helps with anti-aliasing, High Dynamic Range and higher screen resolutions.

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

Pixel Rate: Pixel rate is the most pixels that the graphics card could possibly record to the local memory in one second - measured in millions of pixels per second. The figure is worked out by multiplying the number of Render Output Units by the the card's clock speed. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel rate is also dependant on lots of other factors, especially the memory bandwidth - the lower the bandwidth is, the lower the ability to get to the max fill rate.

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