This is true. Though the 860m is not a 75W part (desktop 750TI is 60W). Generally according to notebookcheck and 45W quad + 860m will draw around ~90W under 3dmark and ~140W under prime+ furmark.
These 15.6" notebooks are generally just over an inch thick.
In real world scenarios you are correct the 860m should never hit 75w and thus the computer need to dissipate that amount of heat. But you forgot two things. On desktop parts they do not count the ram as part of the tdp for nvidia products but to my understanding on laptops they do (this will only be a few watts though).
The second thing is even if the real tdp is less Nvidia has to create "baskets" where there product can be easily placed in a whitebox laptop. The oems will not redesign an alienware case or a lenovo y50 case for it was 65, 70, or 75 watts they will just round up and go with the lowest one that meets the requirements.
Nvidia has the sub 50watt design with the gtx 850m which is the same chip but with lower clocks, but for the higher chip since oems have their cases design for 75 instead of 60 nvidia states the tdp is 75 watts even if really isn't so the oems are confident it can sustain those boosts states and not throttle if they use a 75 watt solution.
Yeah, I know, but my point is would you actually consider one if you're not a gamer or needed it for some other niche purpose?
Those things are monsters, and have lousy battery life. They are more like mobile desktops these days, in relation to the current generation ultrabooks, and ultrabooks are where the technology is headed... except for gaming and niche usage.
I said graphics and I gave a going up scale from ultrabooks to desktop replacements that weigh 6 to 8 lbs. One thing I think of when I hear the word graphics with laptops is either gamers, but also graphic renders and video conversion.
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Personally I hate gaming laptops, for me it is a ultrabook or tablet on the go and my 27" 1440p monitor with a desktop at home. That said these type of laptops do have a point. If I need to travel or do work on the goal that need this type of horsepower (for example I am an engineer). I can get roughly 73 to 80% of the desktop cpu i7 performance in a laptop now, and these laptops can be cheap. On gpu performance desktops though will blow laptops out of the water but even then you can still get nice gpu to do most things. the gtx860m maxwell part is a wonderful piece of silicon. In theory I can do the same type of works I normally do at home with a good enough laptop connected to my 27" monitor and my screen just turn off.
Personally I want to see this happen.
- Most people: Core M from Pentium to 5Y series. Now the Pentium Haswell U weree 1.1 ghz with the 10w chip and 1.7 ghz with the 15w chip so I hope they release something in the 1.5 ghz for the 4.5w chip eventually but intel may decide atom is close enough and they want to upscale you. Said mainstream computers come from 10" to 15" normal laptops possibly even a 17." Focusing on cost, weight, battery life, good screen, some form of ssd. Sure a 35w cpu would be faster but for these people's task the cpu is fast enough, it is the form factor, the battery life, the screen, the storage speed that need the real improvement and going with a lower tdp cpu allows you to make it fanless, thin, gives you more space for battery, etc.
- Cheap Gamers and people who still want something small but more power could easily happen with a 28w Dual Core with the onpackage edRAM. Last time intel only had the edram on their 47w+ plus models but there is no reason they can not put it on a dual core 28w model. 28w models allow you to make something macbook retina size without going extremely expensive. In this form factor you get limited gains with going nvidia or amd gpu vs just using the intel edRAM solution if intel made it available (you would get better drivers with nvidia). This is the form factor that would benefit the most from edRAM (that and servers but that is a different matter).
- Professionals who need hefty computing power and Heavy Gamers will go for the 45 watt cpu models like normal, and dedicated graphics. These skus honestly do not need the edRAM sure it would be nice but if intel wants to save some money they could.