ATI Mobility Radeon HD 4850 vs NVIDIA Quadro K620M

ATI Mobility Radeon HD 4850

The ATI Mobilty Radeon HD 4850 from AMD is a DirectX 10.1 upper middle-class notebook graphics adapter. Technically, the GPU is based on the desktop HD 4850 GPU but with a lower clock rate for reduced energy consumption.

The gaming performance of the ATI Mobility Radeon HD 4850 should be comparable to the desktop HD 4830 and is therefore very good at resolutions below 1080p. The high amount of shaders and the wide 256 bit bus can allow the card to run practically every DirectX 9 game in high resolutions and details. Demanding DirectX 10 games, such as Crysis, can be played with medium to high detail settings. Compared to an Nvidia GeForce GTX 260M, the HD 4850 should be a bit faster on average.

The newer Mobility HD 5850 is noticeably faster than the Mobility HD 4850 if GDDR5 graphics memory is present. If DDR3 with a smaller 128 Bit memory bus is used instead, then this would bottlebeck the 5850 to performance levels closer to that of the Mobility HD 4850.

The mobile HD 4850 core is based on the RV770 chip and features 800 stream processors (or 160 5-dimensional shader cores). These cores do the graphics work previously done by dedicated shader and pixel pipelines of older GPUs. The stream processors (also called ALUs) are grouped in five-way VLIW units. Each of the five instructions of a VLIW bundle has to be independent from the others, so the overall performance is highly dependent on driver optimizations.

The Mobility Radeon HD 4850 includes UVD 2, Avivo HD software and an onboard soundchip for 7.1 sound output over HDMI or DisplayPort. UVD 2 supports full bitstream decoding of H.264/MPEG-4 AVC and VC-1 streams by the GPU, thus reducing workload from the CPU. In addition to this, the software also supports dual video stream decoding and Picture-in Picture mode for full compliancy to the UVD BD-Live standards. Simply put, the Avivo HD technology is able to handle most video tasks and enables the GPU to decode HD videos.

AMD has claimed a current consumption of about 45-65 Watt for the cards part of the mobile HD 4850 to HD 4870 range. Still, it is unclear if this value represents the core chip alone or the entire MXM board with memory modules. We estimate that the VRAM chips would contribute about 5 Watts total to the overall energy demands of the mobile HD 4850.

Compared to the desktop ATI Radeon HD 4850, the mobile 4850 features a slower core clock and is therefore more similar to the desktop HD 4830 in terms of overall performance.

NVIDIA Quadro K620M

The Nvidia Quadro K620M is a DirectX 11 and OpenGL 4.5-compatible graphics card for mobile workstations. It is a Maxwell-based GPU built on the GM108 chip with 384 shader cores and manufactured in 28 nm by TSMC. The Quadro K620M is the successor to the significantly slower Quadro K610M. Usually, the GPU comes with 2 GB DDR3 memory clocked at 1000 MHz (2000 MHz effective, 16 GB/s). 

The Quadro series offers certified drivers that are optimized for stability and performance in professional applications like CAD or DCC. OpenGL performance, for example, should be significantly better than with GeForce graphics cards of similar specifications.

Architecture

Compared to Kepler, Maxwell has been optimized in several details to increase power efficiency. Smaller Streaming Multiprocessors (SMM) with only 128 ALUs (Kepler: 192) and an optimized scheduler should lead to better utilization of the shaders. Nvidia promises that a Maxwell SMM with 128 ALUs can offer 90% of the performance of a Kepler SMX with 192 ALUs. GM108 features 3 SMMs and thus 384 shader cores, 24 TMUs and 8 ROPs (64-bit interface).

Another optimization is the massively enlarged L2 cache. The larger size can reduce some of the memory traffic to allow for a relatively narrow memory interface without significantly hurting performance.

GM108 supports DirectX 11.2 (feature level 11.0 only) as well as DirectX 12.

Performance

Due to their identical specifications, the Quadro K620M offers a similar 3D gaming performance as the consumer GeForce 840M. Most games from 2014/2015 will run fluently in low or medium settings. Compared to other Quadro GPUs, the K620M performs almost similar to the older K1100M.

Features

The feature set should include support for up to 4 active displays. High-resolution monitors of up to 3840x2160 pixels can be connected using DisplayPort 1.2 or HDMI 1.4a (HDMI 2.0 not supported). 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.

Using CUDA or OpenCL, the cores of the Quadro K620M can be used for general calculations.

GM108 integrates the sixth generation of the PureVideo HD video engine (VP6), offering a better decoding performance for H.264 and MPEG-2 videos. Of course, VP6 supports all features of previous generations (4K support, PIP, video encoding via NVENC API).

Power Consumption

The power consumption of the Quadro K620M should be about 30 W including the board and memory components. Therefore, the GPU is best suited for laptops 13 - 14-inches in size and above. The K620M also supports Optimus to automatically switch between an integrated graphics card and the Nvidia GPU.