The Half speed PCI-e bus.
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On the next day I noticed that CPU-z and GPU-z report the PCI-e link on the motherboard is capable of x16 v2.0 but is running ar x8 v2.0. For a moment I felt that there might be a problem with the Graphic card or the motherboard. I went through the BIOS and checked every option to make sure that some option related to the PCI-e link is causing the problem. Every thing seemed to be fine in the BIOS (BIOS updated to 1207). GPU-z still reported x8. For a moment I wondered if there is any power saving feature at play dynamically reducing the link width. But I am not aware of any
such thing. So I ran a Furmark in burn mode and checked if there is any change in the link width. No luck, both GPU-z and CPU-z reported the same link width. So power saving features causing this is ruled out.
Than I googled and found that there are other people also with various other hardware setups facing the same problem. Some of the posts said that if the Bandwidth is reported properly then there is no need to worry. The Bandwidth that GPU-z reported with my card seemed to be proper, but I am still not convinced that x8 is OK. I searched some more and found a forum post which said that graphic card not inserted properly may cause this problem. So I opened up the case and verified if the card is inserted properly. It is properly inserted, but to be sure i removed the card and re-inserted it securely. Then I ran GPU-z and bang this time it showed v2.0 x16 @ x16 v2.0, even CPU-z concurred. The card is very long (10.3 inches), so i thought even if it looked properly inserted for the first time, it may indeed be a problem of graphics card not inserted properly.
Update: The next day While running 3DMark vantage, I noticed that my GPU score is significantly less than what is expected. GPU score of GTX 260 SP216 is supposed to be above 9000, and mine is a XXX edition with 640/1000/1380. So I was expecting some kind of improvement but definitely not a decrease in score. I got a GPU score of 8050. The CPU score is OK. Then I opened GPU-z and the link width is again reported as x8 v2.0. I was about the open the case to
check if the graphic card is properly inserted, but thought I will just restart and check. To my relief after the restart both GPU-z and CPU-z reported x16 v2.0, touch wood. I am not sure why this happened again. I will keep a watch on this. Then I ran 3DMark vantage in performance preset, but no luck this time also the GPU score is exactly the same. I spent some 6.5 hours on this into the wee hours of the night (from 10.30 PM till about 4 A.M). Check the section "lower than normal 3DMark Vantage scores" under benchmarks below to know what fixed this.
Lower than normal 3DMark vantage scores:
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Then I ran 3DMark vantage. To my surprise GPU score is lower than where my card should be. I got 8050 on the GPU score, whereas it should be above 9000. The CPU score seemed fine, but the overall is again less because of the lesser GPU score. I spent a lot of time trying to figure out what may be causing the problem. I ran the test with physX support disabled in the nvidia drivers, but the score is still the same. While searching for solutions, someone pointed out that the 190 series has issues with 3DMark Vantage and overall 186.16 Forceware driver is better.
Its time to get Forceware 186.16. I downloaded and installed this driver and ran 3DMark vantage P test again with GPU PhysX disable in nvidia drivers. Bingo, the GPU score shot up to 9850 and the total score is also where it should be. I am getting approx 10% boost in GPU score because of the 10% factory over-clock. Now everything is fine, touch wood.
. Cleaning the graphic card might have helped. Game on.