Shadow flickering in Portal/HL2 - Why? (YouTube video included)


Jul 8, 2002
I'm running on XP Pro SP2 with 163.71 drivers and 7800GTX SLI.

I've tried all the different settings for shadows but still get the problem you can see in the YouTube video:

Oddly, when I boot into my Vista drive, I do not get this problem... but because of Vista... I can't play the game in surround sound so am opting for my XP install.

Any ideas what might be causing this?

I get it in all flavors of HL2 (i.e. Portal, TF2, etc.)

Thanks for helping as I REALLY want to play...

Try disabling SLI in your drivers, reboot, and check your game again. I have been having a similar issue in many games for the last few driver releases. If I run w/ 1 card, the problem goes away, but w/ SLI I have texture flickering in some games. Yes in UT2k4, WoW. No in Bioshock and DDO. Haven't played HL series in a while though I just bought ep2 last night, and will check to see if I have this issue in this game.

Cards and system check out OK, and if I switch back to any of the 9x.xx series of drivers, the problem also goes away.
Change the SLI profile to use SFR. Nvidia default for HL2 is AFR and this seems to cause the flickering shadow problem w/SLI set-ups and the newer drivers.

or at least that's what worked for me (XP Pro/163.71 and 7800GT SLI).
Change the SLI profile to use SFR. Nvidia default for HL2 is AFR and this seems to cause the flickering shadow problem w/SLI set-ups and the newer drivers.

or at least that's what worked for me (XP Pro/163.71 and 7800GT SLI).

Doh! I wish I read your post earlier to give this a try.

Instead, I went Standpoint's route and disabled SLI and sure enough, it worked! So I upgraded to the latest beta 163.76, and re-enabled SLI and same problem.

So... I *downgraded* to 93.71, enabled SLI... and flickering gone!

Then I saw your post... :eek:

When I get the courage, I'll give it a try.

Currently with the 93.71 drivers, I'm getting framerates generally above 30 running 3840x1024 with no AA and 8x AF. Sometimes it dips into the low 20's with big Portal rooms.

I saw similar frames with 163.71.... so not sure if it is worth messing with at this point.

Thanks everyone for the help on this one!

Well.... decided to give it a go so I uninstalled the 93.71's & re-installed the 163.76's.

Problem returned and, unfortunately, switching to SFR rendering did not fix it. :(

So I went back to the 93.71's.....

One question though: I thought that the load balancing bar for SFR was a horizontal line through the center of the screen that moved up and down as load changed. When I switched to SFR via nHancer (after making a duplicate profile and manually activating it), the load balancing bar was the same as AFR's i.e. the thick green vertical bar on the left side of the screen.

Was this changed in a driver version to be the same.... or is it possible that the SFR profile was not activating?


Sounds like it didn't really go to SFR to me. Also had the same thing with SLI and Source games.
Yeah, sounds like it didn't switch to SFR. Try to "force SFR" through the HL2 profiles (there's a bunch of them, and I set each to force SFR) in the nvidia control panel/drivers. Also, I'm running 163.71 and not 163.76, so there may be some sort of difference there, and I've only used this on HL2 (ep1, ep 2 and lost coast).

When I first had this problem after "upgrading" to 163.71, I also went back to 93.71, but then I found this solution in another forum and it worked for me. Honestly, I haven't noticed any real performance difference. Some people have commented that the IQ is a little better with 163.71, but I haven't really noticed that either.

The other solutions I came across are switching to a pre-163 driver (which we know works) or switching shadow details to low (which I didn't really want to do and didn't try anyway since the SFR thing worked).
Im glad to see Im not the only one with this issue. I think this problem only happens for those w/ 7800series cards. I will try the rendering fix this week and see if it works for me.

The problem w/ the 93.71 drivers is that they do not have some of the graphics qualities that the newer drivers have for newer games. A great example is to run Bioshock w/ the 93.71 drivers. It looks on my system like a completely different game.

Im hoping that a future nvidia driver release will finally put this problem to rest.
I have this exact problem with a 7900 GT CO and it would start to flicker so all I would do is save the game and reload and it would be fixed, I only had to do this once or twice throughout gameplay but its STILL annoying.
I have this problem as well. I didn't notice it in portal (got to about level 16 so I played quite a time) and didn't notice it in Team Fortress 2 until I upgraded to the beta drivers on I did notice it in Episode 2 though. One thing I've noticed about the nzone beta drivers is that performance also seems much lower. I guess I'll have to give the 93.71 drivers a try. Times like these I really wish ATI was a match for nvidia these days.
performance seems lower with the 93 drivers than the current ones on the nvidia site.

Don't install the 93.xx drivers if you intend on trying to go back to the 163.xx drivers. For whatever reason, doing this completely destroys the ability to use the new control panel in the 163.xx drivers. It's impossible to fix even using driver sweeper. Nvidia is terrible. I really wish ATI had a better offering this year :(
I was able to use the new control panel after switching back and forth from the 93.71 to the 163.71 drivers.

Played at a LAN this weekend and noticed that my flickering issue cropped up in TF2, and blinking shadows in HL2ep2.

Bummer. I think I'm going to wait around to play HL2ep2, hope a new driver fixes this.
Wow, I was pulling my hair out last night with almost the same issue. Not shadow related for me but the whole screen was flickering. I'm using 163.75's on Vista 32-bit. I was using "Alternate frame rendering 1" and then switched to "split frame rendering". This is where it got weird. The top half of my screen was a tad bit darker than the bottom (you could see the draw line where each card took over) and the flickering was gone. So in my case it's that the colors of each card are not quite the same and when alternate frame rendering is active it appears to flicker. Gonna try an older driver solution tonight.

This was with Titan Quest: Immortal Throne. The only game I have currently installed.
I read that the 7 series SLI bug is fixed with the latest beta 169.01 drivers.