Radeon, Frame Latency, And New Drivers - AVS Forum
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post #1 of 17 Old 01-29-2013, 02:36 PM - Thread Starter
 
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http://techreport.com/news/24285/catalyst-13-2-beta-with-frame-latency-improvements-now-available?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+techreport%2Fall+%28The+Tech+Report%29

It has become apparent over the last year that one of the many problems with AMD's video drivers is a frame latency issue. As you've seen me discuss around here lately, we want every frame to come in under 16ms to hit 60fps, and that is still kinda hard to do. We've hit the 60fps average and even minimum point pretty easily, so now it's time to look at framerates on a per-frame basis.

The short of it is that AMD's drivers have had a bit of a stutter issue when it comes to latency. To oversimplify and provide an example: Radeons will render a frame in 5ms, followed by a frame in 20ms at a pretty regular interval. These new drivers are finally a step in the right direction in attempting to average that out. In this example, that 5ms and 20ms frame have a goal of rendering each frame instead at 13ms. The result is that each frame would be new for a 60hz update instead of "new new repeat; new new repeat". Again, obvious oversimplification, but the concept scales.

How about Nvidia? This is yet another example of Nvidia skating to where the puck is going. They've been working on frame latency for the last two years. They saw us coming up on "60fps is easy" so they shifted over to a latency focus before being prompted by outside forces. That's what happens when you spend as much as needed on a driver team instead of starving your driver team.
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post #2 of 17 Old 01-31-2013, 01:04 AM
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I installed the 13.2 beta and there was a noticeable difference in how smooth Skyrim is on my 7970. I'm glad that AMD is finally addressing frame latency, but it shouldn't have taken this long.
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post #3 of 17 Old 01-31-2013, 01:31 AM - Thread Starter
 
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I've had sudden long days at work the last couple days, but shortly I plan on playing Skyrim with the current 12.11 (?) drivers, then loading up the 13.2 drivers. I wonder if they work well enough that the default pre-tweak judder is even reduced. I look forward to these improvements. smile.gif
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post #4 of 17 Old 01-31-2013, 02:49 AM - Thread Starter
 
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Through my experimentation Radeon judder in Skyrim is maybe a bit reduced on these new drivers, but it is still nowhere near the smoothness of using an external utility to enforce a 60fps cap. I am on a 6870 though, and word is that frame latency judder is more of a problem on 7000 series cards. Also too, Skyrim is a bit of a weird one, so I guess we'll wait and see how AMD's latency initiative progresses in other titles.

kai - Follow the advice in post #2 here if you want to see how smooth Skyrim is supposed to be:

http://hardforum.com/showthread.php?t=1667639

MSI Afterburner is the free piece of software that you'll need to go with that advice. smile.gif

http://event.msi.com/vga/afterburner/download.htm
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post #5 of 17 Old 01-31-2013, 12:54 PM
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thanks james. it did seem smoother with the frame limiter. i guess amd hasn't fixed it completely yet.
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post #6 of 17 Old 02-04-2013, 02:58 PM
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Quote:
Originally Posted by darklordjames View Post

TFollow the advice in post #2 here if you want to see how smooth Skyrim is supposed to be:

http://hardforum.com/showthread.php?t=1667639
I installed MSI Afterburner and I'm trying to follow the instructions in that post. I can't figure out how to "enable OSD" and "Create a keyboard shortcut to OSD".
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post #7 of 17 Old 02-04-2013, 03:26 PM - Thread Starter
 
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Let me write up some better directions! smile.gif

1) Download MSI Afterburner. It doesn't matter if you have an MSI product or AMD/Nvidia. http://event.msi.com/vga/afterburner/download.htm

2) Install Afterburner, but don't run it. We don't care about Afterburner itself. We care about a utility that comes bundled with it.

3) Find you Afterburner install folder. Inside of that is a Bundle folder, then OSDServer. For me this is here: C:\Program Files (x86)\MSI Afterburner\Bundle\OSDServer

4) Find RTSSWrapper.exe iside this folder. Create a shortcut to that, and stick it on your Desktop or Quicklaunch bar.

5) Run this RTSSWrapper. Turn Start With Windows to On. Show OSD to Off. Hit the Wrench icon to go to settings. Check Start Minimized. Find the Framerate Limit option on first settings page and set it to 60.

6) (Optional) Minimize the program. You should have a little Dove icon in your System Tray with a purple 60 on it.

7) Run Skyrim. Notice how the nasty Radeon judder is now gone. Yay! I find the easiest way to tell the difference is to look at a sharply lit item and slowly pan left and right. With the 60fps limiter the motion is smooth. Without the limiter the item seems to jump in it's panning with more common stalls.

My best guess is that Skyrim renders frames as quickly as it can, regardless off your Vsync settings. So even though you are set to vsync 60hz, it tries to render more frames anyway. Then, still guessing based on it's performance, it just throws away any extra frames that it rendered.

Assume for a minute that you are running 100fps, or frames take 10ms to render. Normally a 60hz game will start a new frame render at a smooth cadence of 0ms, 16ms, 33ms, 50ms, 67ms, 83ms, 100ms, etc. The 6ms between the 10ms render time and the 16ms display time is spent waiting. Skyrim's behavior implies that it will show you rendered frames that started rendering at the earliest possible time resulting in a weird cadence. In example frames will render at 0ms, 10ms, 20ms, 30ms, etc. The 10ms increments and 16ms increments don't match up though, so you see the frames from timestamp 0ms, 10ms, 30ms, 50ms, 60ms, 80ms, 100ms. Note the weird jump between 10ms and 20ms delays between frames instead of a constant smooth 16ms. The result is 60fps gameplay that feels like every third frame is dropped.

We can only hope that Bethesda bought id so that they'll finally have a good engine to build on.
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post #8 of 17 Old 02-04-2013, 03:43 PM
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Like the engine Rage was built on? wink.giftongue.gif


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post #9 of 17 Old 02-04-2013, 03:52 PM - Thread Starter
 
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Which is an amazing piece of technology. The way they scale assets and resolution to maintain a perfect 60fps, combined with a very smart implementation of adaptive vsync is brilliant. It launched in poor condition, but worked great a week later. It launched in perfect condition on the 360 and remains the finest console example of maintaining a smooth 60fps on at all times.
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post #10 of 17 Old 02-04-2013, 04:31 PM
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Quote:
Originally Posted by darklordjames View Post

Which is an amazing piece of technology. The way they scale assets and resolution to maintain a perfect 60fps, combined with a very smart implementation of adaptive vsync is brilliant. It launched in poor condition, but worked great a week later. It launched in perfect condition on the 360 and remains the finest console example of maintaining a smooth 60fps on at all times.

Good point. I should try it on the new computer I built with a GTX670. I've also turned on the adaptive v-sync. I think I still see tearing though. frown.gif


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post #11 of 17 Old 02-04-2013, 04:54 PM
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Let me write up some better directions! smile.gif
Thanks. Those instructions are much better.

I didn't have any complaints with Skyrim. But after doing this things like running water and smoke seem to look better at first glance.
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post #12 of 17 Old 02-05-2013, 12:13 PM
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Good point. I should try it on the new computer I built with a GTX670. I've also turned on the adaptive v-sync. I think I still see tearing though. frown.gif

That is how adaptive VSync works. Only run VSync above 60fps. It is supposed to provide a smoother experience than frame limiting though.
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post #13 of 17 Old 02-05-2013, 02:09 PM
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It "works" by being worse than regular v-sync? When regular v-sync is working, you won't see tearing but the framerate is inconsistent. Adaptive v-sync is supposed make that inconsisent framerate go away. Not add more tearing. wink.gif

I guess my framerate isn't high enough! Need more powah!


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post #14 of 17 Old 02-05-2013, 03:09 PM - Thread Starter
 
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Driver-based adaptive vsync is a bit of a kludge. It's better to have the option than to not, but it requires more tweaking on the user's end to use properly. With classic vsync you want all frames to come in under 16ms, resulting in a perfect 60fps. Any time you miss that 16ms limit with something like a 20ms frame, it then has to wait until the next screen update to apply the new image. The result is that the previous frame sits on the screen for twice as long. It's a 30fps frame inside your 60fps motion. Ideally you'll be rendering at an average ~8ms, so that when you have dips they still only dip down to ~15ms. Even then you'll still have long 20ms frames on occasion. This is where driver-based adaptive vsync works best. You get torn frames, but the tear will normally be in the top 20% of the screen where it isn't as noticeable, and only for a couple of frames before your rendering comes back to sub-16ms levels.

If you are noticing the tearing, the tear is running through the center of your screen, or the tearing is going on for longer than tenths-of-a-second, then you need to tweak settings down a bit. The trap is that if you get caught in areas where the render time hits 25ms for one frame, then every following frame takes 15.5ms, you can get caught in a loop where a group of 15.5ms frames will all have tears in them as they each only add 1ms of time to compensate for the one frame that was 9ms late. The end result is that while only one frame was late, a group of 10 frames end up with tears. 1/6th of a second worth of tears is noticeable. Drop settings a bit, get your average framerate up a bit, and see if the tearing becomes less of an issue. The end goal is motion that feels perfectly smooth, without noticeable tearing, and without the judder that you get by dropping frames when you have a +16ms frame in your 60hz update.

Now, Rage: Rage handles adaptive vsync in software and it is brilliant about it. Rage keeps track of how long frames are taking to render. When a frame hit the 15ms range, it starts doing things like loading in lower level of detail models, running lower resolution shader effects, loading lower quality distance textures, and as a last resort it drops the resolution on the fly. The result is that since it has an active tracking system for render time, it can ensure that it gets as close as possible to hitting that 16ms goal every time. In the cases where it does miss the 60hz update with a 17-18ms frame, it drops vsync, the tear is in the top 10% of the frame where nobody will notice it, and the tear only last for a couple of frames. By the forth 17ms frame or so, enough lower quality stuff has loaded in that the render time comes back in under the 16ms goal and vsync locks back up. When the render time drops back down in to the 12ms range, higher quality models start loading back in.

It's the difference between an passive and an active frame time monitoring system, and it is genius. More games should follow it's lead. I still hold that driver-based adaptive vsync is preferable to drivers that do not have the option, but it takes a bit more effort on the user's part to get it running in an acceptable manner. The end result does give you better motion than 60hz with 30hz judders though.
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post #15 of 17 Old 02-05-2013, 03:31 PM
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That explains why Rage would go from looking great to looking bad on the 360. I didn't really care for the game anyways though.
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post #16 of 17 Old 02-05-2013, 04:41 PM - Thread Starter
 
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"That explains why Rage would go from looking great to looking bad on the 360"

You must have been playing a different version of the game than I was. Maybe you had the Chinese knock-off "Dage"? It was extremely rare that I actually noticed the drop in character or shader detail, and I never noticed the drop in resolution. 10% less detail here and there keeps it well within the range that humans don't notice the difference in things. I guess I also had mine installed to a 16GB flash drive.

The 360 was the premier platform for that title, and it showed. The game ran unbelievably well on (at the time) 6 year old hardware.
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post #17 of 17 Old 02-05-2013, 05:47 PM
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I played from disc. Admittedly this causes problems with a lot of games.
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