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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 speed at 600 MHz. The GDDR3 memory is set to run at a speed of 900 MHz on this particular model. It features 112 SPUs along with 56 Texture Address Units and 16 ROPs.

Compare all of that 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 features a 128-bit bus, and makes use of a 28 nm design. It is comprised of 384 SPUs, 32 Texture Address Units, 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

As far as performance goes, the GeForce 9800 GT 1GB should in theory be a bit superior to the GeForce GT 640 DDR3 overall. (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 a bit (about 17%) better at 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

The GeForce GT 640 DDR3 is quite a bit (more or less 50%) more effective at anti-aliasing than the GeForce 9800 GT 1GB, and also will be able to handle higher resolutions more effectively. (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: Memory bandwidth is the maximum amount of information (counted in MB per second) that can be transferred across the external memory interface in one second. The number is worked out by multiplying the card's interface width by its memory speed. If it uses DDR type RAM, it should be multiplied by 2 again. If DDR5, multiply by ANOTHER 2x. The higher the card's memory bandwidth, the faster 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 can be processed per second. This number is worked out by multiplying the total number of texture units by the core speed of the chip. The higher the texel rate, the better the card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed in a second.

Pixel Rate: Pixel rate is the most pixels the graphics card can possibly write to the local memory per second - measured in millions of pixels per second. The figure is calculated by multiplying the amount of Raster Operations Pipelines by the clock speed of the card. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel fill rate also depends on quite a few other factors, especially the memory bandwidth - the lower the memory bandwidth is, the lower the ability to reach the maximum fill rate.

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