What is the difference between desktop and mobile graphics cards?

Can someone explain the difference between a mobile and desktop card? The only difference I notice is the m after the model number.

 

There is no M after the model number anymore. However when they used to:

The chips have different numbers of CUDA cores, different amounts of VRAM etc... They aren't really that similar at all. The 10 series is closer though. The 1060 for example is pretty much the same for both laptop and desktop just clocked lower on the laptop with a lower tdp.

 

Now they're just pretty much adjustable TDP for different scenarios. So a 1070 isn't always the same as another 1070... brilliant Nvidia... brilliant!

 

Differences have accounted for much more than just the 'm' insignia after the model number.

For example, the Nvidia GTX 970M is nowhere near as fast as desktop GTX 970M.
At best, the 980M may come close to desktop 970M.

However, with Pascal and Polaris iterations of GPU's... it would seem that most of the specifications of the GPU's remain the same between desktop and mobile cards.
However, on Nvidia's end, most 1060's for laptops seem to be clocked lower than the desktop counterparts... and despite that in most OEM laptops, they seem to be at best just as fast as 980M or slightly slower (apparently due to inadequate cooling issues).
Only the Clevo brand of laptops managed to get away without any kind of thermal problems and their 1060's in laptops are 30% faster than 980M (Maxwell).

On AMD's end, they are releasing E9550 soon which has identical specs to the desktop RX 480 in ALL areas (number of Stream Processors, ROP's, base and boost clock speeds - everything is identical), however, the TDP on the E9550 is down to 95W (vs 120 [undervolted] /150W for desktop RX 480) thanks to binning and improvements to the manufacturing process.

So (at least for now) it would seem that on the AMD end, there would not appear to be ANY differentials between desktop and laptop version of GPU's.
Nvidia technically does have desktop Polaris in notebooks, but their clock speeds if I'm not mistaken are NOT the same... and their mobile parts perform slower than desktop ones.

 

Actually the laptop 1070 has a higher core count then the desktop 1070 (2048 vs 1920).

It's just clocked lower.

 

If there was going to be a Pascal M series, the 1080M would be the current 1070. All they did was rename them, so they match their desktop counterparts more closely.

The 1080 now in laptops is not all that different than what we saw with the 980 last year. Except last year they had the old names.

 

they simply changed their names, so that they better represent their current offerings vs desktop. Past GPUs use similar naming scheme for both desktop and laptops, but they treated both markets as completely independent. This is why their 980m was, for example, their highest end GPU for a while. But it had nothing to do with the desktop 980 in name. Just as the 980 was the highest end for a while.

Now, since they have low enough TDP, they are trying to name them in a consistent manner to the desktop world. Notebook GPUs for the 1060 and 1080 use the same GPU core, just adjusted voltage and clocks. The 1070 notebook variant is a different GPU core but its performance and specs are similar to the desktop 1070 so they named it that way.

Originally, there was going to be Pascal M series like previous gens. The 1070 is the remained or that plan, because it was supposed to be the usual mobile GPU upgrade, supposedly a 1080M. But nvidia changed its plans, so they adapted it. They already had created the GPU and it was already inside laptops. So they simply renamed it.

Now, unlike desktops, the name means little because everyone can put a 1080 where they want. That doesn't mean it will perform as it should.