So yeah, I think torture tests are perfectly valid.
Yes, I think most agree that torture testing with Furmark for say overclocking stability is valid. However, going back to your car analogy, they test cars in the
real world (i.e, on public roads, in Nevada dessert, in cold climates, etc.). Therefore, if you took the car to the same places, it's going to work without issues.
However, we are talking about using Furmark to
measure power consumption. You can't ever achieve the same power consumption with any game. In other words, with Furmark you are testing the power circuitry of the videocard and its ability to sustain stability beyond real world load conditions - and that's fine for component testing for a peace of mind. Therefore, while Furmark is good for stress testing, it shouldn't be used as a gauge of power consumption.
Again, let's look at the definition of TDP.
"The TDP is typically
not the most power the chip could ever draw, such as by a power virus, but rather the
maximum power that it would draw when
running real applications."
^^^ By this very definition, Furmark will exceed TDP ratings for most videocards. What has changed after HD4870 series is AMD revised the driver so that Furmark no longer loads the cards the same way. In other words HD4870 cards had no driver protection, so they would be unrealistically loaded to 100%.
NV uses "gaming load" when listing its TDPs, whereas ATI uses "Furmark load" when listing its TDPs.
AMD has improved the detection of FurMark and OCCT by adding a more serious technique based on the
ratio of texture to ALU instructions. In other words, AMD is doing everything in its power to not allow Furmark to load its cards to 100% - AMD did this to protect its valuable customers from videocard failures.
Blastingcap, the idea that AMD is much closer to TDP in Furmark is not very important because besides the software driver protection mentioned above, AMD went 1 step further and
has enabled PowerPlay protection in hardware starting with HD58xx series.
"For Cypress based cards, AMD has hard-wired the protection and has implemented a hardware solution to the VRM problem, by dedicating a very small portion of Cypress’s die to a monitoring chip. This chip monitors the VRM. If the chip detects a dangerous situation (overload), the chip will immediately throttle back the card by one PowerPlay level."
Therefore, one cannot compare the Furmark loads on HD4870 vs. HD5870/68xx series because Furmark no longer works the same way on modern AMD videocards. I applaud AMD for doing this because Furmark does not realistically load the GPU's power circuitry anyways.