NVIDIA GeForce GT 625M vs NVIDIA GeForce GT 640M
NVIDIA GeForce GT 625M► remove
The NVIDIA GeForce GT 625M is an entry-level, DirectX 11 compatible graphics card that was announced in the third quarter of 2012 for laptops. Compared to the older GeForce GT 620M, it is a higher clocked version of the chip. The 620M can be based on either the 40nm GF108 chip (similar to the GeForce GT 525M) or the new power-optimized 28nm GF117 chip with 64-bit or 128-bit DDR3 memory. Both architectures still stem directly from the Fermi generation. Therefore, both versions are also possible for the GT 625M.
It should be noted that the 28nm version of the GT 620M does not offer dedicated graphics ports and can therefore only be used in conjunction with Optimus.
The GF117 is based on the optimized GF108 Fermi chip (GeForce GT 540M) and offers 96 shaders, 16 TMUs and 4 ROPs. Each shader core is clocked twice as fast as the rest of the graphics chip, a technique known as hot clocking. More detailed information on Fermi can be found on the GT 435M GPU page.
The performance of the GT 625M depends on the Turbo clock in the used laptop but should be on average a bit above the average GT 620M. Therefore, the card is suited for casual gamers as demanding games of 2012 may only run in low detail settings fluently.
The shader cores (also called CUDA cores) can be used for general calculations with APIs such as CUDA, DirectCompute 2.1 and OpenCL. PhysX is theoretically possible, but the GT 625M is too slow to handle both PhysX and 3D rendering for modern games. 3D Vision is not supported according to Nvidia.
NVIDIA GeForce GT 640M► remove
The NVIDIA GeForce GT 640M is a mid-range, DirectX 11.1 compatible graphics card that was announced in the first quarter of 2012 for laptops. It is a Kepler-based GPU built on the GK107 architecture and is manufactured in 28nm at TSMC. The graphics card uses a 128-Bit wide memory interface with either the more common but slower DDR3 for VRAM or the more expensive and faster GDDR5.
The Kepler architecture is the successor to the Fermi architecture that first appeared in laptops with the GeForce 400M series. The GK107 Kepler core offers two shader blocks, called SMX, each with 192 shaders for a total of 384 shader cores that are clocked at the same speed as the processor core. Although more shader cores are available in the Kepler architecture as compared to the Fermi design, the Kepler shaders are still expected to be up to twice as power efficient. However, due to the missing hot clock of the shader domain, two shaders of a Kepler chip are as fast as one shader of a Fermi chip (the latter is clocked twice as fast). PCIe 3.0 is now supported by the mobile Kepler series and an optional Turbo mode can automatically overclock the Nvidia card by a theoretical 15 percent if the laptop cooling system allows it. The implementation of this boost mode is done in the BIOS, but it is ultimately dependent upon the manufacturer of the laptop.
The gaming performance of the GeForce GT 640M equipped with DDR3 graphics memory lies somewhere in the former 2011 high-end category between the older GeForce GT 555M and GeForce GTX 460M. The performance is exceptionally good in shader-heavy DirectX 11 games and benchmarks. However, the 128-Bit memory interface can be a bottleneck if DDR3 graphics memory is used. In our tests, demanding games of 2011 like Battlefield 3 are playable in 1366x768 and medium settings. Less demanding games, such as Modern Warfare 3, are easily playable with maxed out settings and high resolutions. Details on synthetic and gaming benchmarks performances of the GT 640M can be seen below. The more uncommon GDDR5 version of the GT 640M is slightly faster, getting closer to the DDR3 version of the GT 650M.
The improved feature set now includes support for up to 4 active displays. Furthermore, high resolution monitors of up to 3840x2160 pixels can now be connected using DisplayPort 1.2 or HDMI 1.4a if available. HD-Audio codecs, such as Dolby TrueHD and DTS-HD, can be transmitted via bitstream mode through the HDMI port. However, as most laptops will feature Optimus, the integrated GPU will likely have direct control over the display ports and may limit the feature set available by the Nvidia Kepler cards.
The 5th generation PureVideo HD video processor (VP5) is also integrated in the GK107 core and offers hardware decoding of HD videos. Common codecs such as MPEG-1/2, MPEG-4 ASP, H.264 and VC1/WMV9 are fully supported up to 4K resolutions while VC1 and MPEG-4 are supported up to 1080p. Two streams can be decoded in parallel for features such as Picture-in-Picture. Another novelty is the inclusion of a dedicated video encoding engine similar to Intel QuickSync that can be accessed by the NVENCI API.
The power consumption of the GeForce GT 640M is a bit below that of the older GeForce GT 540M and more in line with the GT 525M. As a result, the Nvidia GPU is best suited for multimedia notebooks 14-inches or greater.
|NVIDIA GeForce GT 625M||NVIDIA GeForce GT 640M|
|GeForce GT 600M Series|
|96 -||384 -|
|Core||625 MHz||625 - 645 (Boost) MHz|
|Memory||1800 MHz||1800 - 4000 MHz|
|Bus||64 Bit||128 Bit|
|Max. Memory||1024 MB||2048 MB|
|DirectX||DirectX 11, 5.0||DirectX 11, 5.0|
|Technology||28 nm||28 nm|
|Features||PhysX, Verde Drivers, CUDA, Play, Optimus||Optimus, PhysX, Verde Drivers, CUDA, 3D Vision, 3DTV Play|