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GeForce 9800 GT 1GB vs GeForce GT 640 DDR3

Intro

The GeForce 9800 GT 1GB uses a 65/55 nm design. nVidia has clocked the core frequency at 600 MHz. The GDDR3 RAM works at a frequency of 900 MHz on this model. It features 112 SPUs as well as 56 Texture Address Units and 16 Rasterization Operator Units.

Compare all of that to the GeForce GT 640 DDR3, which comes with a clock speed of 900 MHz and a DDR3 memory frequency of 1782 MHz. It also features a 128-bit memory bus, and makes use of a 28 nm design. It is comprised of 384 SPUs, 32 TAUs, and 16 ROPs.

(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% quicker than the GeForce GT 640 DDR3 in general, due to its greater data rate. (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 little 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 a lot (approximately 50%) faster with regards to AA than the GeForce 9800 GT 1GB, and able to handle higher resolutions without losing too much performance. (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 (in units of MB per second) that can be transported past the external memory interface in one second. The number is calculated by multiplying the card's interface width by its memory clock speed. If the card has DDR RAM, the result should be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The higher the card's memory bandwidth, the better the card will be in general. It especially helps with anti-aliasing, HDR and high resolutions.

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

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

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