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Differences What are the advantages of each

Front view of Radeon HD 6400

Reasons to consider the
AMD Radeon HD 6400

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Lower TDP 18W vs 65W 3.6x lower TDP
Front view of GeForce GT 640

Reasons to consider the
Leadtek GeForce GT 640

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Higher clock speed 902 MHz vs 625 MHz Around 45% higher clock speed
Slightly higher memory bandwidth 28.8 GB/s vs 12.8 GB/s 2.2x higher memory bandwidth
Higher texture rate 28.86 GTexel/s vs 5 GTexel/s More than 5.8x higher texture rate
Slightly better floating-point performance 692.7 GFLOPS vs 200 GFLOPS Around 3.5x better floating-point performance
More render output processors 16 vs 4 12 more render output processors
More texture mapping units 32 vs 8 24 more texture mapping units
More shading units 384 vs 160 224 more shading units
Wider memory bus 128 bit vs 64 bit 2x wider memory bus
Higher memory clock speed 900 MHz vs 800 MHz Around 15% higher memory clock speed

Features Key features of the Radeon HD 6400  vs GeForce GT 640 

memory bandwidth Rate at which data can be read from or stored in onboard memory

Radeon HD 6400
12.8 GB/s
GeForce GT 640
28.8 GB/s

pixel rate Number of pixels a graphics card can render to the screen every second

Radeon HD 6400
2.5 GPixel/s
GeForce GT 640
7.22 GPixel/s

texture rate Speed at which a graphics card can perform texture mapping

Radeon HD 6400
5 GTexel/s
GeForce GT 640
28.86 GTexel/s

floating point performance How fast the gpu can crunch numbers

Radeon HD 6400
GeForce GT 640
692.7 GFLOPS

shading units Subcomponents of the gpu, these run in parallel to enable fast pixel shading

texture mapping units Built into each gpu, these resize and rotate bitmaps for texturing scenes

Specifications Full list of technical specs


Radeon HD 6400  vs
GeForce GT 640 
GPU brand AMD Nvidia
GPU name Caicos LE GK107
Market Desktop Desktop
Clock speed 625 MHz 902 MHz
Is dual GPU No No
Reference card None Nvidia GeForce GT 640 902 MHz 2 GB

raw performance

Shading units 160 384
Texture mapping units 8 32
Render output processors 4 16
Pixel rate 2.5 GPixel/s 7.22 GPixel/s
Texture rate 5 GTexel/s 28.86 GTexel/s
Floating-point performance 200 GFLOPS 692.7 GFLOPS


Radeon HD 6400  vs
GeForce GT 640 
Memory clock speed 800 MHz 900 MHz
Effective memory clock speed 1,600 MHz 1,800 MHz
Memory bus 64 bit 128 bit
Memory 512 MB 1,024 MB
Memory type GDDR3 DDR3
Memory bandwidth 12.8 GB/s 28.8 GB/s

noise and power

TDP 18W 65W

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