GeForce GT 640 DDR3 vs GeForce GTS 450

Intro

The GeForce GT 640 DDR3 uses a 28 nm design. nVidia has clocked the core frequency at 900 MHz. The DDR3 RAM runs at a frequency of 1782 MHz on this card. It features 384 SPUs as well as 32 TAUs and 16 Rasterization Operator Units.

Compare that to the GeForce GTS 450, which comes with core speeds of 783 MHz on the GPU, and 902 MHz on the 512 MB of GDDR5 memory. It features 192 SPUs along with 32 TAUs and 16 Rasterization Operator Units.

Price Comparison

Specifications

Memory Bandwidth: Memory bandwidth is the maximum amount of data (counted in megabytes per second) that can be transferred across the external memory interface in one second. It's calculated by multiplying the interface width by its memory speed. If the card has DDR type RAM, it should be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The better the memory bandwidth, the better the card will be in general. It especially helps with anti-aliasing, High Dynamic Range and high resolutions.

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

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