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GeForce 9800 GT 1GB vs GeForce GT 640 DDR3

Intro

The GeForce 9800 GT 1GB features a core clock frequency of 600 MHz and a GDDR3 memory frequency of 900 MHz. It also makes use of a 256-bit bus, and uses a 65/55 nm design. It features 112 SPUs, 56 Texture Address Units, and 16 ROPs.

Compare that to the GeForce GT 640 DDR3, which comes with clock speeds of 900 MHz on the GPU, and 1782 MHz on the 2048 MB of DDR3 memory. It features 384 SPUs along with 32 TAUs and 16 Rasterization Operator 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

As far as performance goes, the GeForce 9800 GT 1GB should in theory be a little bit better than the GeForce GT 640 DDR3 in general. (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 is just a bit (about 17%) more effective at texture 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

The GeForce GT 640 DDR3 is much (more or less 50%) more effective at AA than the GeForce 9800 GT 1GB, and also able to handle higher screen resolutions better. (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 largest amount of data (measured in MB per second) that can be moved past the external memory interface in one second. It is calculated by multiplying the card's bus width by its memory speed. If it uses DDR type RAM, the result should be multiplied by 2 once again. If it uses DDR5, multiply by ANOTHER 2x. 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 can be applied in one second. This is calculated by multiplying the total amount of texture units of the card by the core speed of the chip. The better the texel rate, the better the 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 the video card could possibly write to the local memory per second - measured in millions of pixels per second. The figure is worked out by multiplying the number of Raster Operations Pipelines by the clock speed of the card. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel output rate is also dependant on quite a few other factors, most notably the memory bandwidth - the lower the bandwidth is, the lower the ability to get to the maximum fill rate.

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