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Radeon HD 3870 1GB vs Radeon R9 M275X

Intro

The Radeon HD 3870 1GB features a core clock speed of 775 MHz and a GDDR4 memory frequency of 1125 MHz. It also features a 256-bit memory bus, and makes use of a 55 nm design. It features 320(64x5) SPUs, 16 Texture Address Units, and 16 ROPs.

Compare those specs to the Radeon R9 M275X, which comes with a clock speed of 900 MHz and a GDDR5 memory speed of 1125 MHz. It also makes use of a 128-bit memory bus, and makes use of a 28 nm design. It is comprised of 640 SPUs, 40 Texture Address Units, and 16 Raster Operation Units.

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon R9 M275X		50 Watts
Radeon HD 3870 1GB		106 Watts
	Difference: 56 Watts (112%)

Memory Bandwidth

Both cards have exactly the same bandwidth, so theoretically they should have the same performance. (explain)

Texel Rate

The Radeon R9 M275X is much (about 190%) faster with regards to anisotropic filtering than the Radeon HD 3870 1GB. (explain)

Radeon R9 M275X		36000 Mtexels/sec
Radeon HD 3870 1GB		12400 Mtexels/sec
	Difference: 23600 (190%)

Pixel Rate

If using lots of anti-aliasing is important to you, then the Radeon R9 M275X is a better choice, but only just. (explain)

Radeon R9 M275X		14400 Mpixels/sec
Radeon HD 3870 1GB		12400 Mpixels/sec
	Difference: 2000 (16%)

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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Radeon HD 3870 1GB

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Radeon R9 M275X

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Specifications

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Model	Radeon HD 3870 1GB	Radeon R9 M275X
Manufacturer	AMD	AMD
Year	Nov 19, 2007	May 1 2014
Code Name	RV670 XT	Venus XTX
Memory	1024 MB	2048 MB
Core Speed	775 MHz	900 MHz
Memory Speed	2250 MHz	4500 MHz
Power (Max TDP)	106 watts	50 watts
Bandwidth	72000 MB/sec	72000 MB/sec
Texel Rate	12400 Mtexels/sec	36000 Mtexels/sec
Pixel Rate	12400 Mpixels/sec	14400 Mpixels/sec
Unified Shaders	320(64x5)	640
Texture Mapping Units	16	40
Render Output Units	16	16
Bus Type	GDDR4	GDDR5
Bus Width	256-bit	128-bit
Fab Process	55 nm	28 nm
Transistors	(Unknown) million	(Unknown) million
Bus	PCIe 2.0 x16/AGP 8x	PCIe 3.0 x16
DirectX Version	DirectX 10.1	DirectX 11.2
OpenGL Version	OpenGL 3.0	OpenGL 4.3

Memory Bandwidth: Memory bandwidth is the maximum amount of data (measured in MB per second) that can be moved over the external memory interface within a second. It is worked out by multiplying the bus width by its memory clock speed. If it uses DDR memory, it should be multiplied by 2 again. If it uses DDR5, multiply by ANOTHER 2x. The higher the memory bandwidth, the better the card will be in general. It especially helps with AA, High Dynamic Range and high resolutions.

Texel Rate: Texel rate is the maximum texture map elements (texels) that are applied per second. This is worked out by multiplying the total texture units of the card by the core 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 applied in one second.

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

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