Strange CPU Scaling with Rift

I'm seeing something strange in the way CPU usage scales when I'm adding additional accounts to my team in Rift. I recognize there's always a limit to what any machine can run and if I've hit mine, that's fine. I'm just hoping for a little insight as to why the scaling is working as it seems to be.

First a little background. I recently built a new gaming machine. It's pretty much a monster and has eaten up and spit out anything I've thrown at it. Below are the main specs:


Processor: Intel(R) Core(TM) i7-2600K CPU @ 3.40GHz (8 CPUs), ~3.4GHz -> water-cooled and oc'd to a very stable 4.5 GHz.
Memory: 16384MB RAM
2 x NVIDIA GeForce GTX 570, SLI'd
Video cards and memory are vendor oc'd

So with that out of the way.

I've been 5-boxing with great performance. Running my background toons on low and my main on ultra, I'm getting 30-50 fps in Meridian. Using the standard core allocation from the guide on this site, my average cpu usage is 50-60% with a pretty even distribution between cores, although my 1-2 pair does see a bit higher usage than the other cores.

My gpu's aren't even breaking a sweat. I find it very strange however, that changing the settings on my primary toon from Ultra to Medium has very very little impact on my fps.

So, to experiment, I added a sixth account. I used a core allocation as follows:

1/2 - slot 1
3/4 - slot 2, 3
5/6 - slot 4, 5
7/8 - slot 6

With six toons running, I'm still getting good performance. My average cpu usage hovers around 65% with only half my physical ram allocated and still plenty of headroom for my gpu's.

Now, here's where it gets weird.

I added a 7th toon using this allocation:

1/2 - slot 1
3/4 - slots 2, 3
5/6 - slots 4, 5
7/8 - slots 6, 7

Considering the minimal performance impact in going from 5 to 6 toons, I expected 7 to scale in a simlar fashion. What's happening is completely different though. As soon as the 7th toon loads, my cpu cores all peg, my fps drops to about 5 and my gpu's are barely in use.

There's obviously a bottle-neck of some sort there, but it just doesn't make any sense to me why the sudden jump. I've experimented with several alternative core allocations. I've tried the running the 7th process outside of ISBoxer. Same result. Seems the 7th toon used several times the resources that the 6th one did. If 6 is all I can run, that's fine. I'd just like some insight as to why the scaling is as it is.

Can anyone enlighten me? Thanks in advance.

Edit: Added a screenshot of 6 accounts running : https://picasaweb.google.com/1108997373 ... 1464955970

Core allocation:
1/2 - slot 1
3/4 - slot 2, 3
5/6 - slot 4, 5
7/8 - slot 6, 1

[lax]

Link doesn't work

The only thing that comes to mind is if you're hitting a RAM limit, probably on the master video card. Lowering your resolution or reducing other graphics settings will reduce that impact, and using the video cards separately likely would as well.

Thanks for the quick reply. This should be a good link: https://picasaweb.google.com/lh/photo/b ... directlink

You're probably right about the video memory. That's the only thing I hadn't considered and it makes some sense. Everything else I could monitor seemed to have significant headroom left. I will try to find out if there's a good way to monitor that.

As far as de-SLI'ing my cards, I have tried that as well. I was running on multiple monitors, but have changed to a single very big monitor. I get a significant performance increase with the cards SLI'd. I know this hasn't always been the case but maybe the drivers have improved or something.

Oh and while I have your attention, your VideoFX tools are unbelievable. For the numbers in my first post, I turned them all off, but I usually run with a significant number of VideoFX and the performance hit is very small.

[MiRai]

I get...

Oops... there's nothing to see here. Either you do not have access to these photos, or they don't exist at this web address. Please contact the owner directly to gain access.

...on both links.

You're probably right about the video memory. That's the only thing I hadn't considered and it makes some sense. Everything else I could monitor seemed to have significant headroom left. I will try to find out if there's a good way to monitor that.

GPU-Z

Sorry about the links. For the first time in years I find myself without my own online storage so I attempted to upload those to a picassa album real quick. Guess that didn't work so well.

The screenshot isn't really that important because LAX nailed it. It's video memory. WIth 6 sessions running my gpu's are both under 40% utilization but my video memory is close to 90%.