AMD Frame Pacing Explored: Catalyst 13.8 Brings Consistency to Crossfire
by Ryan Smith on August 1, 2013 2:00 PM ESTThe Test
For the purposes of our testing we’ll be looking at the 6 games we’ve adopted for use with FCAT due to their proven reliability. These are Total War: Shogun 2, HItman: Absolution, Sleeping Dogs, Battlefield 3, Bioshock Infinite, and Crysis 3. All of our results unless otherwise noted are using Catalyst 13.8b1 for the AMD cards, and NVIDIA’s 326.19 beta drivers for the GeForce cards.
Our metric of choice for measuring frame times and frame pacing is a metric we’re calling Delta Percentages. With delta percentages we’re collecting the deltas (differences) between frame times, averaging that out, and then dividing delta average by the average frame time of the entire run. The end result of this process is that we can measure whether sequential frames are rendering in roughly the same amount of time, while controlling for performance differences by looking at the data relative to the average frame time (rather than as absolute time). This gives us the average frame-to-frame time difference as a percentage.
In general, a properly behaving single-GPU card should have a delta average of under 3%, with the specific value depending in part on how variable the workload is throughout any given game benchmark. 3% may sound small, but since we’re talking about an average it means it’s weighed against the entire run, as the higher the percentage the more unevenly frames are arriving. For a multi-GPU setup we’d ideally like to see the delta percentages be equal to our single-GPU setups, but this is for the most part unreasonable. There is no hard number for what is or isn’t right here, but based on play testing we’d say 15%-20% is a reasonable threshold for acceptable variance, with anything under 10% being very good for a multi-GPU setup.
Finally, in our testing we did encounter an issue with Catalyst 13.8 that required we make some slight adjustments to FCAT to compensate for this bug, so we need to make note of this. For reasons we can’t sufficiently explain at this time but has been confirmed by AMD, in some cases in Crossfire mode AMD’s latest drivers are periodically drawing small slices of old frame buffers at the top of the screen. The gameplay impact is minimal-to-nonexistent, but this problem throws off FCAT badly.
To quickly demonstrate the problem, below we have two consecutive frames from one of our Battlefield 3 runs. The correct FCAT color order here is dark blue, green, light blue, and olive. The frames corresponding to dark blue and green occur on frame one, and light blue and olive on frame two. Yet looking at frame two, we see a small 6 pixel high stripe of dark blue at the very top of the image. At this point the dark blue frame should have already been discarded, as the cards have moved on to the green and later light blue frames. Instead we’re getting a very small slice of a frame that is essentially 2 frames old.
The gameplay impact from this is trivial to none; the issue never exceeds a 6 pixel slice, only occurs at the top of the frame (which is generally skybox territory), and is periodic to the point where it occurs at most a few times per minute. And based on our experience this primarily occurs when a buffer swap should be occurring during or right after the start of a new refresh cycle, which is why it’s so periodic.
However the larger issue is that FCAT detects this as a frame drop, believing that over a dozen frames have been dropped. This isn’t actually possible of course – the context queue isn’t large enough to hold that many frames – and analysis shows that it’s actually part of the old frame as we’ve explained earlier. As such we’ve had to modify FCAT to ignore this issue so that it doesn’t find these slices and count them as dropped frames. The issue is real enough (this isn’t a capture error) and AMD will be fixing it, but it’s not evidence of a dropped frame as the stock implementation of FCAT would assume.
Ultimately our best guess here is that AMD is somehow mistiming their buffer swaps, as the 2 frame old aspect of this correlates nicely to the fact that the dark blue and light blue frames would both be generated by the same GPU in a two-GPU setup.
| CPU: | Intel Core i7-3960X @ 4.3GHz |
| Motherboard: | EVGA X79 SLI |
| Power Supply: | Antec True Power Quattro 1200 |
| Hard Disk: | Samsung 470 (256GB) |
| Memory: | G.Skill Ripjaws DDR3-1867 4 x 4GB (8-10-9-26) |
| Case: | Thermaltake Spedo Advance |
| Monitor: | Samsung 305T |
| Video Cards: |
AMD Radeon HD 6990 AMD Radeon HD 7970GE AMD Radeon HD 7990 NVIDIA GeForce GTX 590 NVIDIA GeForce GTX 680 NVIDIA GeForce GTX 690 |
| Video Drivers: |
NVIDIA ForceWare 326.19 AMD Catalyst 13.5 Beta 2 AMD Catalyst 13.6 Beta 2 AMD Catalyst 13.8 Beta 1 |
| OS: | Windows 8 Pro |
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anubis44 - Friday, August 2, 2013 - link
TheJian, you seem to be suffering from verbal diarrea. You might want to take some immodium for that.What you could have said in about 1/10th the space is: you harbour an inexplicable hatred for Ryan Smith, because he's ever said anything positive about an AMD product, and that you think that despite AMD's huge stride forward in one driver revision to address and fix a problem with multi-GPU crossfire smoothness (let's face it, a fairly obscure problem, too), nothing AMD will ever do will be good enough for you, because you harbour an inexplicable hatred of AMD, too.
There, I summarized your entire rant in one sentence. Short and sweet. Concision is bliss.
TheJian - Tuesday, August 6, 2013 - link
https://en.wikipedia.org/wiki/Ad_hominemPlease review the chart from Graham, then come back with something at the top of his pyramid instead of the bottom :)
You seem to be suffering from the inability to make a coherent response to a valid argument, thus attack me instead :) It's always amusing to see fanboys flounder when faced with the facts (no matter if I argue for or against a company, it happens on both sides).
I own a radeon 5850...ROFL. I don't care about NV and will state they suck when or if they do. There is a reason I bought the 5850 :) The only thing I hate about AMD is management taking a total dump on one of my favorite companies (probably mostly due to spending all the R&D on consoles, thus screwing my PC choices and driving them directly into the ground). Having said that, I'll buy maxwell next unless something is terribly wrong with it if only for money backing the drivers. You can google my posts here and see I've been begging people to STOP asking AMD for price cuts and free games so they will start making money. I have done this MANY times. I'm not looking forward to NV owning the gpu world and making it too expensive for me to upgrade as much as I please.
No fan of Ryan or Anandtech these days. I'd hope their alexa traffic numbers forces them to start acting like they did pre Sept last year (which are off by half, as people see the points I and others make). People are not being fooled.
transphasic - Tuesday, August 6, 2013 - link
Excellent points, and well said!The AMD fanboy sure is a grumpy one when their feelings get hurt at the fact that their beloved company has DROPPED the ball AGAIN for the hundredth time.
The loudly proclaim to the world that they finally recognize a problem with their CF setup, and have supplied a minor tweak here and there to get a few games fixed, and that we as AMD owners should start cheering loudly for all through the night.
LOL. It has taken them forever to finally see a problem, and then they take forever to fix it after all this time, even when it hasn't been fixed.
AMD reminds of me Kramer from Seinfeld, who tells Jerry that he will give back to him the pliers he borrowed (that he also broke into pieces and destroyed) but only when Jerry does what he wants him to do, and in so doing, makes Jerry feel like he should be happy about it.
Like Kramer, AMD tries in vain to make us very happy about something that should already had been fixed long ago- just like their Enduro nightmare which STILL after 18 months has not be fixed, and when they do come out with a PARTIAL and incomplete fix- as is THEIR obligation after these many years, we are told to feel happy that we at least got SOMETHING.
They took almost 2 1/2 months to come up with a minor fix for some games, and it's still only Beta, and those with single CPU setups got nothing, all the while Nvidia keeps cranking out the WHQLs, and improved Drivers for a wide variety of games- including AMD-based games.
There's a REASON why AMD is so much cheaper, and far less expensive than Nvida GPU's and Intel CPU's, and we all know why- crappy drivers that are slow to come out, poor attention to detail, weak performance across the board on all their product lines, and a lack of motivation about fixing the problems in a timely manner that they chose to ignore in the first place.
As the saying goes, you get what you pay for...
TheJian - Friday, August 2, 2013 - link
"Ultimately we have to give AMD the kudos they deserve. They have come forward about their issues"No we don't have to give kudos to a company with a beta product who hasn't even fully fixed it yet today. It's like shipping cars with 3 tires. Kudos to the company for putting on a 4th tire for the users today...Seriously? NO WAY. And since it doesn't fix everything (XP users see nothing, eyefinity again nothing), it's really just a 4th tire that is FLAT still...ROFL. They didn't come forward either. They were FORCED INTO THE LIGHT. See PCper's comments in my previous post. They told them he was wrong 1/2 dozen times...ROFL. That isn't coming forward, it's denying you have issues.
"For users who have a reasonable level of faith in Crossfire scaling and are satisfied with AMD’s frame pacing improvements, a $799 7990 is a very good deal at the moment."
If you're stupid enough to still believe BEFORE seeing, well you get what you deserve ;) He keeps printing stuff like this. We're not talking Jesus Christ here (whom I guess you need faith in forever right?), this is a company who can't seem to fix problems that have been dogging them for years (not just since april - they've been claiming they had no problem as hardocp shows this is why NV created FCAT to prove AMD wasn't stutter free for years). They still wouldn't discuss the issues with PCper that are ongoing.
"When I asked AMD for more details on WHY Eyefinity wasn't fixed with this release and why it technically was presenting more of a problem, they didn't want to get into it."
Shouldn't they be coming forward with what is going on? Still hiding:
http://www.pcper.com/reviews/Graphics-Cards/Frame-...
" My theory still revolves around the compositing engine that AMD is using for CrossFire and the amount of bandwidth it can handle. Moving a fame of 2560x1600 pixels 60 times a second is taxing but 5760x1080 uses about 50% more pixels is where things seem to break down for AMD."
Of course 4K won't help this situation as he notes later (I pasted that previously). Be careful if you're just reading anandtech people. Read other sites when AMD vs. NV/Intel is the topic being discussed here. You should NOT buy a A8-5600 as Ian suggests in the 1440p articles for single gpu cards, over Intel. It is foolish as I pointed out in the comments on those articles (and I wasn't alone). I can't believe anyone would recommend AMD over Intel for all but extremely poor people. To recommend it for all single gpu people though is just ridiculous (Titan with a $100 cpu? 780, 7970 etc all show Intel running away BELOW 1440p). I listed the games and links to the articles showing this in the 1440p comments sections. GO LOOK then judge anandtech yourself. I'm not sure what they get promoting AMD, and giving them kudos but I hope it's a LOT of $$. Destroying your reputation isn't worth it IMHO.
DeviousOrange - Friday, August 2, 2013 - link
whine, whine, whine, whine, whine, whine, whine.... yeah you are like a broken record.TheJian - Tuesday, August 6, 2013 - link
But always right :) Thanks for verifying it.gi_ty - Friday, August 2, 2013 - link
Whoa there fella, you shouldn't go out on the internet with your stupidity showing like that.TheJian - Tuesday, August 6, 2013 - link
Personal attacks instead of anything about the data. Shocker.https://en.wikipedia.org/wiki/Ad_hominem
Might want to read that and look in the mirror when done. I don't think you made it out of the pink or orange bar in graham's chart ;)
Come back when you can at least crack the top 3. Then we can talk ;) I'm guessing none of you people took debate class (note I didn't just call you stupid, I'm insinuating you're ignorant) :) It's ok to throw in junk from the bottom of the chart (I'd ignore it anyway most likely) but at least give me something to think about. You know, a valid counterpoint backed by something...Otherwise why bother?
Slugbait - Friday, August 2, 2013 - link
Remember back in the day, when the ideal video setup was a Matrox card paired with a couple of Voodoo2 cards? We were all bashing ATi for their drivers back then.Remember when ATi released the Rage, and it didn't come close to the performance that was advertised? (well...Tom's loved it). ATi said it was because they shipped with beta drivers, because their customers really, really, REALLY wanted the hardware NOW. But every subsequent driver release was "beta", and then they cancelled driver development so they could concentrate on a new line called "Radeon". A lot of people here at Anand's (and FiringSquad, Rage3D, AGN3D, etc) were quite peeved.
Remember when you bought any ATi consumer card for your NT Server machine, only to find out that ATi has never written drivers for NT Server, and you had to use Windows generic drivers (no dual-monitor, etc). Want NT Server support? Buy a FireGL or FirePro.
Remember when your CAD program consistently crashed, but everything was perfectly fine after replacing your ATi card with a card from any other company?
"Catalyst" is often used as a dirty word on the forums here.
They have always known that they write poor drivers. This is not some revelation...this is a public spanking by one of their competitors.
Will they finally wake up and turn things around with their drivers? My confidence is...well, it's kinda low.
boozed - Friday, August 2, 2013 - link
If there're two things I've learned from the internet, it's that Nvidia drivers are terrible, and also ATi drivers are terrible.Meanwhile I've had little trouble with either. Am I doing something wrong?