NVIDIA GeForce GT 635M vs NVIDIA GeForce GT 645M
NVIDIA GeForce GT 635M► remove
The NVIDIA GeForce GT 635M is a fast middle class graphics card for laptops and is essentially a renamed GeForce GT 555M. It is based on the GF108 or GF116 cores with different shader counts, clock speeds and memory configurations. It stems from the Fermi generation and supports DirectX 11 and OpenGL 4.0.
Versions (of the GT 555M):
- 144 cores 709MHz, 128Bit GDDR5, e.g. MSI GX780
- 144 cores 590MHz, 192Bit DDR3, e.g. Dell XPS 17, Alienware M14x
- 144 cores 590MHz, 128Bit DDR3, e.g. Schenker XMG A501 / A701 (Clevo W150HRM / W170HN)
- 96 cores 753MHz, 128Bit GDDR5, e.g. Lenovo Y570p / Y560p
The GF114 and GF116 chips are slightly reworked architectures that were introduced in 2011. Due to a changed transistor design, the clock rates could be higher without increasing overall power consumption. Detailed information on the GF106 can be found on the GeForce GT 555M page and information on the GF104 on the GeForce GT 435M page.
The performance of the GeForce GT 635M is dependent on the version of the card used (see above). The performance range is similar to the former GT 555M and somewhat below the Kepler based GT 640M. Therefore, most modern games run fluently in medium to high settings in 1366x768. Only very demanding games like Metro 2033 or Battlefield 3 will require lower settings (see our benchmark tests below).
A novelty of the GF104/106/108 chips is the support of Bitstream HD Audio (Blu-Ray) output via HDMI. Like the Radeon HD 5730, the GT 635M can transfer Dolby True HD and DTS-HD bitstream to a HiFi receiver without quality loss.
The GT 635M offers PureVideo HD technology for video decoding. The included Video Processor 4 (VP4) supports feature set C and allows the GPU to fully decode MPEG-1, MPEG-2, MPEG-4 Part 2 (MPEG-4 ASP - e.g., DivX or Xvid), VC-1/WMV9, and H.264 (VLD, IDCT, Motion Compensation, and Deblocking). This can free up processing time from the CPU, leading to better multitasking performance.
Furthermore, the GPU is able to decode two 1080p streams simultaneously (e.g., for Blu-Ray Picture-in-Picture).
Through CUDA, OpenCL, and DirectCompute 2.1 support, the GeForce GT 635M can be of help in general calculations. For example, the stream processor can encode videos considerably quicker than can a modern CPU. Furthermore, physics calculations can be done by the GPU using PhysX if supported, such as in Mafia 2 or Metro 2033.
According to Nvidia, the GT 635M supports 3D Vision. It enables the laptop to output 3D content (3D games, 3D Web Streaming, 3D photos, 3D Blu-Rays) to a 3D-enabled screen or an external 3D TV if supported by the laptop manufacturer and when not in conjunction with Optimus.
The relatively high power consumption of the GeForce GT 635M suits it for larger laptops starting from 14-inches. To save power, the card supports Optimus to automatically switch between the integrated Intel graphics card and the Nvidia GPU. Even though the video card natively supports Optimus, it is up to the manufacturer to implement the technology.
NVIDIA GeForce GT 645M► remove
The NVIDIA GeForce GT 645M is a mid-range, DirectX 11.1 compatible graphics card that was announced in the third quarter of 2012 for laptops. It is a faster clocked GeForce GT 640M and therefore also based on the Kepler GK107 architecture 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 645M equipped with DDR3 graphics memory depends on the 3D clock in the used laptop and is slightly above an average GT 640M. Therefore demanding games like Battlefield 3 are playable in 1366x768 and medium settings. Older and less demanding games, such as Modern Warfare 3, are easily playable with maxed out settings and high resolutions.
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 645M should be similar to the GT 640M and therefore 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 635M||NVIDIA GeForce GT 645M|
|GeForce GT 600M Series|
|144 -||384 -|
|Core||660 - 753 (Boost) MHz||710 MHz|
|Memory||1800 MHz||1800 MHz|
|Bus||128/192 Bit||128 Bit|
|Max. Memory||2048 MB||2048 MB|
|DirectX||DirectX 11, 5.0||DirectX 11, 5.0|
|Technology||40 nm||28 nm|
|Features||Optimus, PhysX, Verde Drivers, CUDA, 3D Vision, 3DTV Play|