Radeon HD 4870 1GB vs Radeon HD 4890 1GB

Intro

Compare all of that to the Radeon HD 4890 1GB, which comes with a clock speed of 1000 MHz and a GDDR5 memory frequency of 975 MHz. It also makes use of a 256-bit bus, and uses a 55 nm design. It is made up of 800(160x5) SPUs, 40 TAUs, and 16 Raster Operation Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 4870 1GB		150 Watts
Radeon HD 4890 1GB		190 Watts
	Difference: 40 Watts (27%)

Memory Bandwidth

The Radeon HD 4890 1GB should in theory perform a little bit faster than the Radeon HD 4870 1GB in general. (explain)

Radeon HD 4890 1GB		124800 MB/sec
Radeon HD 4870 1GB		115200 MB/sec
	Difference: 9600 (8%)

Texel Rate

The Radeon HD 4890 1GB is a lot (approximately 33%) faster with regards to anisotropic filtering than the Radeon HD 4870 1GB. (explain)

Radeon HD 4890 1GB		40000 Mtexels/sec
Radeon HD 4870 1GB		30000 Mtexels/sec
	Difference: 10000 (33%)

Pixel Rate

The Radeon HD 4890 1GB will be much (about 33%) faster with regards to full screen anti-aliasing than the Radeon HD 4870 1GB, and also able to handle higher screen resolutions while still performing well. (explain)

Radeon HD 4890 1GB		16000 Mpixels/sec
Radeon HD 4870 1GB		12000 Mpixels/sec
	Difference: 4000 (33%)

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 information (in units of MB per second) that can be moved past the external memory interface in one second. It's calculated by multiplying the interface width by its memory clock speed. In the case of DDR type RAM, it should be multiplied by 2 once again. If DDR5, multiply by 4 instead. The better the memory bandwidth, the faster 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 can be applied per second. This is worked out by multiplying the total texture units by the core clock speed of the chip. The better this number, the better the graphics card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels in a second.

Pixel Rate: Pixel rate is the maximum number of pixels that the graphics card can possibly write to the local memory in one second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the number of ROPs by the the core clock speed. ROPs (Raster Operations Pipelines - sometimes also referred to as Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel rate also depends on many other factors, most notably the memory bandwidth of the card - the lower the bandwidth is, the lower the ability to get to the maximum fill rate.