Radeon HD 4650 1GB vs Radeon HD 7870

Intro

Compare that to the Radeon HD 7870, which features GPU clock speed of 1000 MHz, and 2048 MB of GDDR5 RAM set to run at 1200 MHz through a 256-bit bus. It also features 1280 Stream Processors, 80 Texture Address Units, and 32 Raster Operation Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 4650 1GB		55 Watts
Radeon HD 7870		175 Watts
	Difference: 120 Watts (218%)

Memory Bandwidth

Theoretically speaking, the Radeon HD 7870 should be 586% faster than the Radeon HD 4650 1GB overall, because of its greater bandwidth. (explain)

Radeon HD 7870		153600 MB/sec
Radeon HD 4650 1GB		22400 MB/sec
	Difference: 131200 (586%)

Texel Rate

The Radeon HD 7870 will be quite a bit (approximately 317%) faster with regards to texture filtering than the Radeon HD 4650 1GB. (explain)

Radeon HD 7870		80000 Mtexels/sec
Radeon HD 4650 1GB		19200 Mtexels/sec
	Difference: 60800 (317%)

Pixel Rate

The Radeon HD 7870 will be much (about 567%) more effective at FSAA than the Radeon HD 4650 1GB, and also should be able to handle higher screen resolutions more effectively. (explain)

Radeon HD 7870		32000 Mpixels/sec
Radeon HD 4650 1GB		4800 Mpixels/sec
	Difference: 27200 (567%)

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 (counted in MB per second) that can be moved across the external memory interface in one second. The number is worked out by multiplying the bus width by its memory speed. If it uses DDR type memory, it must be multiplied by 2 again. If DDR5, multiply by ANOTHER 2x. The better the memory bandwidth, 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 amount of texture map elements (texels) that can be applied in one second. This is worked out by multiplying the total texture units by the core speed of the chip. The higher the texel rate, the better the video 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 most pixels that the graphics chip can possibly record to its local memory in a 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 - aka Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel output rate also depends on quite a few other factors, most notably the memory bandwidth - the lower the bandwidth is, the lower the ability to reach the maximum fill rate.