8600M GT in MBP running PCI-E @ x1?

Running a Santa Rosa Macbook Pro 2.4 Ghz in Vista Ultimate.

So a couple days back I installed the new Nvidia mobile 179.28 drivers. Everything seemed fine, though I noticed a fair framerate drop compared to my previous DOX drivers. I decide to play Overlord, which had been running fine the night before, and everything seems perfect until I decide to move into any area with high intensity particle effects or any area with a large number of dynamic lighting/movement. Suddenly the framerate drops to < 1 FPS. If I back out of the area and into citadel main room (central hub of the game), suddenly everything is back to normal. I try cutting all the GFX settings to absolute minimum, but the FPS in certain areas is still less than 3 or 4 FPS when previously it sat around 30.

Must be some issue with the driver, I assume, so I try running Left4Dead and FarCry2 to get a feel for things, they run fine, maybe a 25% decrease in FPS, but certainly not below 1 FPS. I keep hunting, testing results using Overlord, which has the most significant FPS drop. I try disabling and then uninstalling the new PhysX engine, no dice. I try uninstalling the new drivers, safe mode sweeping, and installing my previous drivers, nope. I even try reinstalling Overlord, nada.

Finally, I take my brother's identical Macbook Pro, install the identical Nvidia Driver update, install Overlord, transfer over my save files, replicate maximum GFX settings, enter the problem areas...AND...It runs fine on his system! So what the heck was going on with my system?

I became suspicious of my GPU bandwidth when I considered the area that causes the most issue has a significant amount of moving objects and dynamic lighting, which had initially thrown me off toward the PhysX update. So, I check out the System Info in the Nvidia Control panel, look at my PCI-Express info, and lo-and-behold it is running x1 lane, when on my brother's system it is x16. I downloaded GPU-Z to double check and it reports the Bus Interface as "PCI-E x16 @ x 1". No wonder I am getting massive slowdowns in high intensity areas, I'm getting my bandwidth choked to that of an expresscard slot!

Anyway, anyone have any idea how I might fix this? I considered for a moment that this might just be my 8600M GT failing, which could be possible, though after running the ATI-TOOL Artifact Tester for over 20 minutes, my GPU is at 82 Celsius (normal), and the cube looks fine. I am at a loss, this is an apple computer with EFI so there is no BIOS to go into and tweak the PCI-E lane back to x16. In OSX, system profiler also reports the 8600M GT running at x1, so this is a systemwide issue. Help!

 

My old 9500M GS and my newer 9800M GS both are at x1 on the PCI express usually, but automatically get to 16x when a game starts. leave GPU Z open (altho GPU Z is not reliable by all means) and check after booting an application or game that stresses your GPU. Basically its just like powermizer saving energy by being 1x when not used, so I wouldnt worry about this yet.

try reinstalling the drivers but doing a clean uninstall of your current ones. I also advice getting newer drivers from the 180 family. Uninstall your drivers, clean the traces of old drivers and get full new ones working. If the problem persist, then something might be wrong with the card itself. the 8600m is not a very reliable card.

 

The framerates issue is probably your drivers. Just go back to the ones you had before.

 

Ok I gave it a shot, but GPUZ reports @ x1 mode even while the games are running.

I've already uninstalled these drivers, gone into safemode and run driver sweeper, and tried 178.24, 178.24 Dox, and the newest 181.00 drivers, all have the same issue, and I did a clean install of all of them.

 

UPDATE: I checked out this guy's thread http://forums.macrumors.com/showthread.php?t=424110

Someone else had this problem, THANK GOD! He was able to temporarily and partially solve the problem by shutting down the computer and altering the hardware (removing RAM). I attempted the same thing, except I just removed all peripherals and my external HDD. My PCI-EXPRESS Lane Width now reports x16 @ x8, which means I gained 7 more lanes compared to what I had (x16 @ x1). I am NOT getting my full 16 lanes, but as a test I went back into Overlord, the room that was bringing my system down to < 1 FPS, and it runs very well again! FPS back to normal! Even at half-normal bandwidth I see a SIGNIFICANT performance improvement.

It seems that the PCI-E lane width will reset to x1 every time I restart without altering my hardware, this seems to indicate there is a hardware problem with my computer, does anyone agree?

The OP in the thread I linked found that the only permanent fix was a motherboard replacement. *sigh*

Ah...investigation...you are a cruel mistress.

 

I'm having the same issue. Unplugging peripherals/RAM sometimes works (to get back to 8x), but not always. Anyone have other solutions to this?