GeForce 820M vs Radeon HD 4870 1GB

Intro

Compare those specifications to the Radeon HD 4870 1GB, which comes with a core clock frequency of 750 MHz and a GDDR5 memory speed of 900 MHz. It also uses a 256-bit memory bus, and makes use of a 55 nm design. It is comprised of 800(160x5) SPUs, 40 Texture Address Units, and 16 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce 820M		15 Watts
Radeon HD 4870 1GB		150 Watts
	Difference: 135 Watts (900%)

Memory Bandwidth

As far as performance goes, the Radeon HD 4870 1GB should in theory be quite a bit better than the GeForce 820M in general. (explain)

Radeon HD 4870 1GB		115200 MB/sec
GeForce 820M		16000 MB/sec
	Difference: 99200 (620%)

Texel Rate

The Radeon HD 4870 1GB will be a lot (more or less 161%) faster with regards to texture filtering than the GeForce 820M. (explain)

Radeon HD 4870 1GB		30000 Mtexels/sec
GeForce 820M		11504 Mtexels/sec
	Difference: 18496 (161%)

Pixel Rate

The Radeon HD 4870 1GB will be a lot (approximately 317%) faster with regards to AA than the GeForce 820M, and will be capable of handling higher screen resolutions without losing too much performance. (explain)

Radeon HD 4870 1GB		12000 Mpixels/sec
GeForce 820M		2876 Mpixels/sec
	Difference: 9124 (317%)

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 max amount of information (in units of MB per second) that can be transferred past the external memory interface within a second. It's calculated by multiplying the interface width by its memory speed. If it uses DDR type memory, it should be multiplied by 2 once again. If DDR5, multiply by 4 instead. The better the bandwidth is, the better the card will be in general. It especially helps with AA, HDR and higher screen resolutions.

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

Pixel Rate: Pixel rate is the maximum amount of pixels the graphics card can possibly record to its local memory in one second - measured in millions of pixels per second. The number 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 outputting the pixels (image) to the screen. The actual pixel rate also depends on lots of other factors, most notably the memory bandwidth - the lower the bandwidth is, the lower the potential to get to the maximum fill rate.