How to Compare Desktop Vs Laptop Graphics Cards

It was a hectic few months on the mobile GPU front in the summer months of 2011. NVIDIA was quick to proclaim that they had the fastest laptop GPU on the market in the GeForce GTX 580M, which indeed they had, but not for long.

A few weeks later, AMD let loose a slightly faster Radeon HD 6990M, which at this writing is also less pricey than the GTX 580M–a major setback for NVIDIA and a major leap forward for AMD in other words, but this particular market changes fast and which company has the fastest GPU a year from now is anyone’s guess.

Something that rarely changes, however, and is seldom discussed in any detail is the GPU naming scheme that both of the two leading manufacturers are using. It would be perfectly understandable if a prospective gaming laptop buyer assumes that a GTX 580M is comparable to a desktop GTX 580, but this is far from the truth.

To find out why you only have to look at the specifications. A GTX 580 is equipped with 512 shaders (or CUDA cores as NVIDIA calls them), while the mobile GTX 580M has 384 shaders. The end result according to NVIDIA is a texture fill rate of 49.4 billion/sec for the desktop GPU and 39.7 billion/sec for the mobile GPU.

Now obviously the mobile version is still a very powerful card by any standard, but there’s still a significant difference between the desktop and laptop variants that buyers should be aware of: the actual specifications puts the mobile GTX 580 closer to a desktop GTX 560.

To be fair to NVIDIA, AMD does the same thing. The difference between the desktop HD 6990 versus the mobile HD 6990M is even larger, considering that the desktop card is a dual-GPU solution on one card. In the desktop version, a Radeon HD 6990 graphics card offers an incredible 5.4 TFLOPS of processing power, while its mobile counterpart (in name only) pushes 1.6 TFLOPS and has more in common with the desktop Radeon HD 6870.

There are of course explanations as to why high-end mobile GPUs don’t perform as well as high-end desktop GPUs, and they are quite obvious ones. A gaming desktop computer chassis leaves plenty of room for the power-intensive graphics card to breathe and it can supply hundreds of Watts of power via a large built-in power supply. None of these options are available within the confines of a laptop and it is actually an impressive engineering feat that they are able to perform as well as they do.

It is also somewhat understandable that the manufacturers want to name their most powerful mobile GPUs in a way that they are instantly recognized as their top models. AMD, NVIDIA as well as the gaming notebook manufacturers are also completely upfront with the specifications if you actually read them.

Nevertheless, a first-time gaming laptop buyer often (and understandably) goes by the name of the GPU when shopping for a new system, but may be in for a surprise when he or she starts comparing the specifications.

The intention with this article is not to discourage anyone from gaming laptops; they are high-end machines that will deliver excellent frame rates and visuals in all the latest games in a portable format. It is just a reminder to check the fine print and be aware of the differences.