Sure it is fast enough but you would have to compare it to the NVidea card for that machine for each game to see the difference in heat/load. It only affects how much the GPU is getting used. I have explained it in enough detail, but anyway. You have 5 sp's in a set, but for any game only one will be used in the set for some game elements, but the card still needs to supply full power to them (and has 80% less shaders for each op that requires a fat sp). some games are worse than others.
Effectively for some elements in some games these GPU will be inefficient. For example, from the last page (or another thread, I forget) and that chaps comparison with "Oblivion". Oblivion was playable for me on 3850 OC. If you replace the grass with the high resolution rendered grass mod/patch, then the HDxxxx will ironically have less work to do for the grass as it uses all 5 sp's rather than the one big fat sp for the sprite.
Other examples are Age of Conan (some things are 2D), WOW (spells and smoke and stuff were 2D), Photoshop (or any 2D program).
My guess is that the LoG walls are one humungous hi-res square, rather than lots of little polygons... like most games. Just a guess.
EDIT: here...
http://www.notebookcheck.net/ATI-Mobili ... 073.0.html
Compared to the previous generation such as with the Mobility Radeon HD 4870, the HD 5870 should be about 20% faster
Also, sry it was fallout on the last page (which is oblivion engine I think)... note how he got 78% (ah, nvm I am tired today, it was 100% 78oC on HD3600 which is a pretty low end card) *deleted*. One of the reasons I found was the MADDx5 stuff, although the complexity and CPU also have a large effect in that game. (3850 Overclocked could move more pixels with transcendentals than a 4870, 4870 can do many many more texture fills)
Not all the GPU is used up doing the transcendentals, just a percentage of a percentage if you get what I mean... like if the game had to use 6% (30%) of the GPU on "sprite grass" or moving large surfaces then 24% of the GPU would be wasted, doing nothing (assuming the other 70% was doing other polygon stuff).
EDIT2: Actually it says the Mobility HD 5870 is 20% faster than the Mobility Radeon HD 4870, and I was comparing it to a full 3850/4870, so it would be even worse.
Radeon HD 3850 @ 837MHz Pixel Fill Rate: 13.4 Gigapixels/sec
Mobility Radeon HD 5870 Pixel fill rate: 11.2 Gigapixels/sec
It is slower...
and 11.2 or 13.4 is borderline with VLIW5 as the Fill Rate actually ranging somewhere between 13.4/5= 2.68 and 13.4
As someone pointed out the other solution is to use less pixels... i.e. drop the res to 720p or 768 or something
