GeForce GT 640 DDR3 vs GeForce GTS 450

Intro

The GeForce GT 640 DDR3 has a core clock frequency of 900 MHz and a DDR3 memory frequency of 1782 MHz. It also makes use of a 128-bit bus, and uses a 28 nm design. It is comprised of 384 SPUs, 32 Texture Address Units, and 16 Raster Operation Units.

Compare that to the GeForce GTS 450, which makes use of a 40 nm design. nVidia has set the core frequency at 783 MHz. The GDDR5 RAM runs at a frequency of 902 MHz on this specific card. It features 192 SPUs along with 32 Texture Address Units and 16 ROPs.

Price Comparison

Specifications

Memory Bandwidth: Bandwidth is the max amount of data (in units of megabytes per second) that can be transported past the external memory interface in one second. The number is calculated by multiplying the bus width by the speed of its memory. If it uses DDR memory, the result should be multiplied by 2 once again. If it uses DDR5, multiply by ANOTHER 2x. The better the bandwidth is, 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 number of texture map elements (texels) that are applied per second. This figure is worked out by multiplying the total number of texture units of the card by the core speed of the chip. The better the texel rate, the better the graphics 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 maximum amount of pixels that the graphics card can possibly write to its local memory in one second - measured in millions of pixels per second. The number is calculated by multiplying the amount of Render Output Units by the the core clock speed. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel rate also depends on many other factors, most notably the memory bandwidth - the lower the memory bandwidth is, the lower the potential to get to the max fill rate.