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GeForce 9800 GT 1GB vs GeForce GT 640 DDR3

Intro

The GeForce 9800 GT 1GB makes use of a 65/55 nm design. nVidia has set the core frequency at 600 MHz. The GDDR3 memory works at a frequency of 900 MHz on this model. It features 112 SPUs along with 56 Texture Address Units and 16 Rasterization Operator Units.

Compare those specifications to the GeForce GT 640 DDR3, which comes with a clock frequency of 900 MHz and a DDR3 memory frequency of 1782 MHz. It also uses a 128-bit bus, and uses a 28 nm design. It is made up of 384 SPUs, 32 TAUs, and 16 Raster Operation Units.

(No game benchmarks for this combination yet.)

Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce GT 640 DDR3 65 Watts
GeForce 9800 GT 1GB 105 Watts
Difference: 40 Watts (62%)

Memory Bandwidth

Theoretically speaking, the GeForce 9800 GT 1GB is 1% faster than the GeForce GT 640 DDR3 overall, because of its greater bandwidth. (explain)

GeForce 9800 GT 1GB 57600 MB/sec
GeForce GT 640 DDR3 57024 MB/sec
Difference: 576 (1%)

Texel Rate

The GeForce 9800 GT 1GB should be a small bit (more or less 17%) faster with regards to anisotropic filtering than the GeForce GT 640 DDR3. (explain)

GeForce 9800 GT 1GB 33600 Mtexels/sec
GeForce GT 640 DDR3 28800 Mtexels/sec
Difference: 4800 (17%)

Pixel Rate

If running with a high resolution is important to you, then the GeForce GT 640 DDR3 is superior to the GeForce 9800 GT 1GB, by a large margin. (explain)

GeForce GT 640 DDR3 14400 Mpixels/sec
GeForce 9800 GT 1GB 9600 Mpixels/sec
Difference: 4800 (50%)

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

GeForce 9800 GT 1GB

Amazon.com

GeForce GT 640 DDR3

Amazon.com

Please note that the price comparisons are based on search keywords - sometimes it might show cards with very similar names that are not exactly the same as the one chosen in the comparison. We do try to filter out the wrong results as best we can, though.

Specifications

Model GeForce 9800 GT 1GB GeForce GT 640 DDR3
Manufacturer nVidia nVidia
Year July 2008 June 2012
Code Name G92a/b GK107
Fab Process 65/55 nm 28 nm
Bus PCIe x16 2.0 PCIe 3.0 x16
Memory 1024 MB 2048 MB
Core Speed 600 MHz 900 MHz
Shader Speed 1500 MHz 900 MHz
Memory Speed 900 MHz (1800 MHz effective) 1782 MHz (3564 MHz effective)
Unified Shaders 112 384
Texture Mapping Units 56 32
Render Output Units 16 16
Bus Type GDDR3 DDR3
Bus Width 256-bit 128-bit
DirectX Version DirectX 10 DirectX 11.0
OpenGL Version OpenGL 3.0 OpenGL 4.2
Power (Max TDP) 105 watts 65 watts
Shader Model 4.0 5.0
Bandwidth 57600 MB/sec 57024 MB/sec
Texel Rate 33600 Mtexels/sec 28800 Mtexels/sec
Pixel Rate 9600 Mpixels/sec 14400 Mpixels/sec

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

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

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

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