Radeon HD 4650 512MB vs Radeon HD 6950 2GB

Intro

Compare that to the Radeon HD 6950 2GB, which comes with a clock frequency of 800 MHz and a GDDR5 memory frequency of 1250 MHz. It also makes use of a 256-bit memory bus, and uses a 40 nm design. It is comprised of 1408 SPUs, 88 TAUs, and 32 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 4650 512MB		55 Watts
Radeon HD 6950 2GB		200 Watts
	Difference: 145 Watts (264%)

Memory Bandwidth

As far as performance goes, the Radeon HD 6950 2GB should in theory be a lot better than the Radeon HD 4650 512MB overall. (explain)

Radeon HD 6950 2GB		160000 MB/sec
Radeon HD 4650 512MB		16000 MB/sec
	Difference: 144000 (900%)

Texel Rate

The Radeon HD 6950 2GB will be quite a bit (about 267%) faster with regards to texture filtering than the Radeon HD 4650 512MB. (explain)

Radeon HD 6950 2GB		70400 Mtexels/sec
Radeon HD 4650 512MB		19200 Mtexels/sec
	Difference: 51200 (267%)

Pixel Rate

The Radeon HD 6950 2GB will be much (about 433%) more effective at AA than the Radeon HD 4650 512MB, and also should be able to handle higher resolutions without losing too much performance. (explain)

Radeon HD 6950 2GB		25600 Mpixels/sec
Radeon HD 4650 512MB		4800 Mpixels/sec
	Difference: 20800 (433%)

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 largest amount of data (in units of MB per second) that can be transported across the external memory interface within a second. It is calculated by multiplying the card's bus width by the speed of its memory. If it uses DDR RAM, it should be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The higher the card's memory bandwidth, the better the card will be in general. It especially helps with anti-aliasing, HDR and higher screen resolutions.

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

Pixel Rate: Pixel rate is the maximum amount of pixels the video card can possibly write to the local memory in a second - measured in millions of pixels per second. The number is calculated by multiplying the amount of colour ROPs by the the core clock speed. ROPs (Raster Operations Pipelines - sometimes also referred to as Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel output rate also depends 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.