Hands-On With Nvidia's Titan X (Pascal) In SLI

We test VR, SLI, Nvidia's new high-bandwidth bridges, and the concern that HBM2 might have been a better choice for Titan X.

Introduction

Two Titan X (Pascal) In SLI: Nvidia dropped the GeForce brand too late in development.Two Titan X (Pascal) In SLI: Nvidia dropped the GeForce brand too late in development.

Let me start with what this article is not about. It's not about value. It's not about mainstream (or even enthusiast) gaming. It's not about comparing AMD and Nvidia.

Now that official support for three- and four-way SLI in games is gone, this article is about the pinnacle of performance achievable in late 2016 with Nvidia's Pascal architecture, assuming money is no object.

This article is also about tinkering with really high-end hardware, trying to overclock two Titan Xes in SLI, seeing how they fare in VR, and testing whether the lack of HBM2 (Nvidia opted for GDDR5X instead) is a big deal.

Good Luck Buying One (Or Two)

In order to get my hands on two Titan X cards, I set myself an agenda alert on August 2 to check Nvidia’s online sales page. I checked at midnight. Nothing. I signed up for the "Notify me" email, woke up, and went to work. Still no email. Then I checked at 9:15 AM EST and saw the “Buy Now” button. I took the opportunity and snatched two cards. The notification email arrived about an hour later. Oh, and I totally forgot the new "SLI HB" bridge, so I ended up ordering that separately.

Not long after, Nvidia's online store was out of stock. Since then, we've seen them in and out of stock. But as of October 17th, they're available for purchase from geforce.com. If you’re crazy and lucky enough to get your hands on a pair, consider snagging the SLI HB bridge, too.

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Less SLI Is More SLI

As you no doubt read in our Nvidia GeForce GTX 1080 Pascal Review, Nvidia is curtailing SLI quite a bit. The 1060 doesn't support SLI at all. Moreover, the 1070 and 1080 officially only support two-way configurations in real-world games. The same goes for Titan X. If you were hoping to run three or four of these, you’d have to jump through some hoops. And even then, they’ll only work in approved benchmarks (not games you'd actually play). If you absolutely must try a three- or four-way arrangement in something like 3DMark, you'll need to generate a unique hardware signature using software from Nvidia that can be used to request an “unlock” key.

Last but not least, the Pascal-based boards introduce a new SLI bridge dubbed "SLI HB Bridge," which Nvidia claims "doubles the bandwidth of previous SLI bridges." Technically, you can still use the old "soft" SLI bridges, though.

For reference, the bandwidth of old-school SLI bridges has long been officially quoted as "up to 1 GB/s." At the Pascal launch event, Nvidia mentioned the new SLI bridges supporting a higher pixel clock of 650 MHz (versus the older interface’s 400 MHz), while allowing for a dual-link connection, effectively bringing the available bandwidth in the 3GB/s range for two-way SLI configurations. By comparison, that's less than four lanes of PCIe 3.0 bandwidth.

Nvidia asks you to shell out $40 plus shipping and handling for these, and the company sells them directly on its site. EVGA offers them too.

From an engineering perspective, we really don't care that three- and four-way SLI support was dropped. Based on the multi-GPU rendering technique commonly used (Alternate Frame Rendering), PCs with several graphics cards contend with increased latency, diminishing scaling beyond two GPUs, compatibility issues (especially when it comes to zero-day game support), and a lack of functionality in VR. Particularly given the performance of today’s Pascal-based GPUs, the only way three- and four-way setups make sense is for synthetic benchmarking. Hopefully that means Nvidia will put more effort into improving the current state of two-way SLI.

Furthermore Nvidia continues work on VR SLI as a complement to the single-screen-focused AFR, which needs no more than two GPUs to operate at peak efficiency.

Test System

It would have been great to compare two Maxwell-based Titan X cards to the newer Titan Xes for a generational comparison. Alas, I don’t have two of the older cards on-hand. I did, however, have a couple of EVGA GeForce GTX 980 SCs in SLI.

It goes without saying that the performance jump from 980s to a pair of Titan X cards in SLI is significant in synthetic benchmarks (a full +101.6% in 3DMark Fire Strike’s Graphics Test 2). My remaining tests focus on scaling, overclocking, and other performance characteristics of the Titan X (Pascal).

SLI And VR

Without going into depth on how SLI works (you’ll find more detail in Nvidia's SLI Technology In 2015: What You Need To Know), it primarily utilizes that AFR technology mentioned on the previous page, which imposes a two-frame delay (or queue) to properly provide scaling benefits. And while you won't mind those extra milliseconds on a typical desktop display, an additional 17 ms of motion-to-photon lag in VR will affect your experience.

The workaround for VR is assigning GPUs to specific eyes for stereo rendering acceleration. This naturally requires optimization on the developer’s end, and as a result, SLI just isn’t supported by most VR titles as of mid-2016.

Consequently, we did some testing of the Oculus Rift using the only title we know punishes a GeForce GTX 980, Elite: Dangerous. We’re manually reporting performance based on the in-HMD debug tool display. Unfortunately, Oculus has not responded to our requests to enable logging-to-disk of that tool's data, so we can’t chart that experience out quantitatively.

SLI is disabled in these runs. You can leave the technology turned on in Nvidia's control panel, but the application only exploits one GPU no matter what.


Notice that a single Titan X (Pascal) is barely able to keep up using the Ultra detail preset, with a minimal performance headroom of ~10%. Conversely, a GTX 980 just isn't fast enough to facilitate a smooth experience, averaging 73.1 FPS (below the 90 FPS target), while almost doubling motion-to-photon latency. Not even the Titan X manages to stay below the 20 ms that John Carmack of Oculus describes as the "sweet spot" of VR. You'll have to drop the quality level for an optimal VR experience in Elite: Dangerous for now.

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The Need to Overclock…Your CPU?

I've been using 3DMark Fire Strike as a synthetic benchmark since it came out in 2013. Its "basic" run (non-Ultra and non-Extreme) is pretty taxing on GPUs in its two graphics tests. The other two tests tend to be CPU-bound.

So here's the news: two Titan X (Pascal) cards in SLI are actually CPU-bound in the first graphics test of Fire Strike, though not in the second. And that’s with a Core i7-6700K boosting to 4.2 GHz. Forget about using Unigine Valley or other older tests to saturate the Titan Xes. GPU utilization sits at around 50% in those; the bottleneck is clearly our host processor.

I managed to get the two cards in SLI stable at +190 MHz core and +160 MHz memory, which represents about a +10% overclock. As you no doubt know, clock rates in SLI are synchronized, so your headroom is limited to the less-scalable GPU.

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The Lack Of HBM2 Is No Big Deal

Given AMD’s use of HBM on its Fiji-based cards, hardware enthusiasts are quick to question Nvidia’s lack of HBM2 on the Titan X. The company instead chose to give this card a massive 12 GB of GDDR5X with a nominal memory bandwidth of 480 GB/s. That's a 42% increase over the previous-generation Titan X that offered 337 GB/s.

While it is true that HBM2 facilitates a bandwidth advantage over GDDR5X, the benefits of more throughput would only become apparent in situations where on-die resources aren't being fed fast enough. The concept is akin to PCIe 3.0/2.0/1.1 links between CPU and GPU, and you can already run any modern card with four lanes of third-gen PCIe with little or no performance degradation. Bumping up that bandwidth with eight or 16 lanes yields a 1% to 2% performance increase on average, and anything beyond confers negligible gains.

Below you can see a short run of The Witcher 3 running on two Titan Xes in SLI at 5K (5120x2880p).

Notice that the bottleneck (as you would expect) is on the GPU’s front end. The memory controllers are busy 50-60% of the time, indicating plenty of available headroom with these GDDR5X modules. Would this card be faster if equipped with HBM2 instead of GDDR5X? We down-clocked the memory by -20% and observed a -4% impact on performance in 3DMark. So, more bandwidth might be good for another percentage point or two, at best.

Scaling Is Good At 5K; SLI Is Overkill For 1440p

In games with proper SLI support, you might expect scaling between +70-80% when you add a second Titan X. That’s a fairly typical number in graphics-bound workloads.

Indeed, the Titan X’s SLI scaling falls within that range…unless you’re gaming at 2560x1440, where two GP102-powered cards become CPU-limited. Consequently, scaling pares back to +43% in Total War: Warhammer (a Gaming Evolved title) and +54% in The Witcher 3 (a GameWorks title).

At 5K (2880p), though, the gain is +83% in Total War: Warhammer and +70% in The Witcher 3. In short, you’re overpaying by a ton if your plan is two Titan Xes at 2560x1440. Titan X in SLI is really meant for 4K or 5K displays.

What If We Skip The SLI HB Bridge?

Now, you could argue that if you splurge on $2400 worth of graphic cards, skimping on the $40 SLI HB bridge that supposedly doubles (or even triples) available bandwidth between the cards is a silly thing to do.

And yes, of course, it really would be silly. But as a check of how essential that component may be to Titan X (and also GTX 1080/1070) owners, we decided to run a few tests using an old-school flexible SLI bridge.

The results are interesting. Total War: Warhammer sees absolutely no difference with the low-bandwidth SLI bridge that came with our Asus motherboard, while performance in The Witcher 3 drops from 25% (at 1440p) to 35% (at 2880p) using the flexible connector.

In general, it appears that the $40 SLI HB bridge is worth paying a premium for, even if it doesn’t benefit all games equally.

Conclusion

Assuming you're swimming in cash and lucky enough to catch the Titan X in stock, $2400 gets you the best gaming performance that money can buy.

The card’s scaling in two-way SLI is pretty good; expect 70-80% over a single card (depending on the game) at 5K. If you plan on playing at 1440p (or lower), you’re more likely to see a 40-50% speed-up before your CPU becomes the bottleneck at higher frame rates.

We've also proven that you want that $40 SLI HB bridge on top (something that GTX 1080/1070 owners will appreciate knowing), else you may face a 25 to 35% performance hit in certain games.

For VR, you're better off with just one card at the moment. It'll be a while before developers start taking advantage of multiple GPUs—growth on that front has been slow thus far. Still, a single Titan X is capable of running Elite Dangerous using the Ultra preset at a steady 90 FPS on an Oculus Rift (although motion-to-photon latency is still a sub-optimal 27 ms.)

Whether your rig is a $500 value box with second-hand-parts scavenged off of eBay or a $10,000 behemoth, we'll leave you by the same letters Nvidia inscribed inside the box of the Titan X:

GL HFGL HF

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  • ryguybuddy
    I would like to see another follow-up with Titan X's in a watercool loop and a 6950X or something to see how much of an improvement that would make.
  • clonazepam
    I vaguely remember reading a different article where the two types of SLI bridges were x-rayed and examined much more closely. IIRC, there's very little difference. The newer one has the traces all set to equal lengths (the click of a button in design software), and one pin I think is changed to Ground which allows the driver to detect its presence. I think they're physically equal in otherwise, besides trace length, LED, and the change to ground.

    Anyway, I've done the multiple card setups for many generations, but game development is going in a direction where that's no longer a worthwhile endeavor as support dwindles more and more.

    Thanks for the read.
  • Realist9
    This is an interesting experiment 'for science'. But that's all. SLI support in games is so spotty, unreliable, and sometimes non-beneficial, that it is now, IMO, irrelevant.
  • Compuser10165
    I think going X99 with such a system is a requirement in order to reduce the cpu limit factor. Desite the 10 core 6950X, an OCed 5960X (to about 4.4-4.5ghz) should be enough for such a setup. That is because Haswell -E is easier to OC at higher frequencies versus Broadwell-E.
  • ledhead11
    Thanks for the review. It's nice seeing these SLI reviews especially since there are so few for either the Titan X or 1080's.

    When I got my 1080's I tried the EVGA bridge and had problems with getting full contact on my cards. Some boots would show the cards, some didn''t, so for a time I used dual ribbons until I got the NVidia HB a week or two later. The NVidia worked for me no problem. The main difference I noticed was, a few more FPS here and there but really a more stable, consistent frame rate. I read the same article about the x-ray comparisons as well before purchasing and have to say all this info is getting pretty consistent.

    I can tell you that 1080SLI has very similar performance behavior as to the reviews of Titan X SLI I've seen. Both SLI setups seem to really shine in the 4k/60hz or 1440p/144hz. When I tried DSR 5k on my 4k display the frames quickly dropped to around 40fps.

    I'm not really seeing the CPU bottleneck you mention except for the Firestrike tests. Whether 4k/60hz or 1440p/144hz my 4930k @ 4.10ghz rarely goes above 40%.

    I completely agree with you about what to use the Titan's for- 4k/5k all the way. 1080SLI just starts to hit a ceiling at around 60-80fps in 4k and averages 100-150fps in 1440p depending on the game.
  • ledhead11
    Oh and I forgot to mention, the most noticeable FPS increases with the HB bridge also happened at 4k for me.
  • niz
    I'm very pleased with my (P) Titan X, I upgraded from a 980GTX mostly for VR (Vive) and to be able to play Elite Dangerous at VR Ultra with superscaling set to 2.0, which it does fine now and is so rock solid I just leave SS set to 2.0 for everything in VR. With E:D in VR there's an occasional chugging but it seems to only be during loading screens (i.e. as a result of file I/O) so it seems that theres a real chipset issue that I/O can steal damaging amounts of bandwidth from something (PCIe bus?) rather than the CPU or GPU being maxxed out.
    I have an acer X34 monitor so 3440 x 1440, my PC is running a i7-6700k at stock speed. I keep thinking about blowing another $1200 just to go SLI just because "moar is moar" and just the thought of Titans in SLI give me a nerd boner, but it honestly seems like I'd see no noticeable benefit.
  • RedJaron
    Anonymous said:
    I think going X99 with such a system is a requirement in order to reduce the cpu limit factor. Desite the 10 core 6950X, an OCed 5960X (to about 4.4-4.5ghz) should be enough for such a setup. That is because Haswell -E is easier to OC at higher frequencies versus Broadwell-E.
    Just because a CPU can be clocked higher doesn't mean it performs better. Improvements in IPC and efficiency more often than not make up for the lower clock speeds.
  • somebodyspecial
    Skipped the article after looking at contents. Still waiting on PRO benchmarks for this card to see how it does vs. other top cards in stuff like adobe (cuda vs. amd's OpenCL or whatever works best for them), 3dsmax, Maya, Blender etc. These cards are not even aimed at gamers, so wake me when you test what they were designed to do (pro stuff on the cheap), so content creators have some idea of the true value of these as cheap alternatives to $5000 NV cards (P6000, etc).
  • rcald2000
    + Filippo L. Scognamiglio Pasini
    Since you noticed two Titan XP's achieving only 50% utilization when paired with the i7-6700k, then which overclock CPU would diminish or eliminate that condition? i7-5820k (CPU I own) or an i7-5960X? Any other recommendations would be appreciated. Thank you for the great article.
  • ledhead11
    @rcald2000

    I didn't want to reply directly to your question in case Filippo does answer you.

    Our CPU's are very similar. Most notable differences are 5820k(15mb L3 cache, 28PCIe lanes) and 4930k(12mb L3cache, 40 PCIe lanes). I know 1080's aren't Titan's but they're not that far off. My CPU has yet to go over 60% with both GPU's holding over 95% usage during 4k(60-80fps ultra, vsync on, AA min or off). It mostly averages 40%. This is with ROTTR, Witcher 3, GTA V, DOOM. The most obscene thing I've seen is how ROTTR loves to eat all the ram it can get, where ever it can get it.

    The firestrike physics tests nails it at 100% along with HD video conversions(including software using hardware accelerations).

    That being said. If you're really going all in for 2 of these then I would recommend seeing how your 5820 handles it. My personal experience in going from quads to hexes is that the lower hex speeds are more than compensated by the larger L caches and increased PCIe lanes vs a quad trying to hit 5ghz. I'm actually very surprised how many reviewers still obsess with using quads for these kinds of tests. Just look at the monsters in the 3d mark hall of fame and most are using 6,8,10 cores with their Titan SLI's.

    When I put my old 970's from a 2600k(OC'd 4.20Ghz) to this 4930k(at the time 3.8ghz) I saw an average 10-20FPS increase in 4k. I was using the same memory and hard drives at the time.

    If people are going to try use a quad for 4k/5k 60+hz or 1440p 200hz Titan SLI or the mythical 1080tiSLI(January 2017?) then a quad will likely need to be at ~5ghz or higher(I'm thinking closer to 6). I'm pretty certain a hex or bigger will sit happy around 4-5ghz for this. Mine's at 4.10ghz because I still use all air cool options and I simply don't need more and its 24/7 stable.

    The other thing you may need to do if you take the leap. . .a bigger PSU. 850w can do it but a general recommendation I've heard for optimal PSU efficiency is to double the wattage you need. 2 Titan's and that CPU are going to push real close to 500-600 during a full load. I've watched mine at it averages in the 450-550 as is(but I've also got 2 raids and 3 or 4 other drives and that's including the display as well).
  • rcald2000
    +ledhead11 Thanks for the detailed response.

    ROTTR: I definitely have my eye on this game. One thing that I really respect is how the developer/publisher listed accurate recommended system specs. I also appreciate that they listed two specs: One for 1080p and the other for 1440p. I like titles that are highly optimized, yet push hardware to it's limits. How much RAM have you seen it consume?

    Your recommendation: It honestly didn't occur to me to wait and see how my i7-5820k handles the two GPUs before determining if an upgrade is warranted. I will definitely wait and see. I was also under the impression that a four core high clock rate CPU was a better match for dual high-end GPUs then a six core lower clock rate CPU. I hope that your conclusion is correct, because I really like the extreme processors and I'd like to continue using them.

    bigger PSU: Yes, the 50% of total available power is normally the most efficient part of the curve. Ideally a 1,000 watt Titanium (115V variant) would be a great option for two 250 watt PSU's in SLI with a top tier CPU. I've definitely considered upgrading to either an EVGA 1000 T2, or Seasonic Prime, although the later doesn't yet come in the 1,000 watt version. Honestly you will never recoup the cost of a titanium efficiency PSU over a gold efficiency; it's more of a pride thing.
  • mechan
    Anonymous said:
    Oh and I forgot to mention, the most noticeable FPS increases with the HB bridge also happened at 4k for me.


    Anonymous said:
    + Filippo L. Scognamiglio Pasini
    Since you noticed two Titan XP's achieving only 50% utilization when paired with the i7-6700k, then which overclock CPU would diminish or eliminate that condition? i7-5820k (CPU I own) or an i7-5960X? Any other recommendations would be appreciated. Thank you for the great article.


    Well, first of all - it really is a 1440p issue. At 5k (and, likely, 4k for the matter) you'll see the bottleneck shift to the GPU.

    Now there literately is no reason to push over 150 FPS at 1440p (the most capable displays can handle 144 Hz but no more) so I think the question you are asking is somewhat academic in nature ...

    ... but entertaining the academic question, if GPU utilization is 50% and the bottleneck is on the CPU, you're looking to a 100% overclock required (per queuing network theory) to shift the bottleneck to the GPUs. Needlessly said, a 100% CPU overclock (let alone a stable one) is essentially impossible in any conventional environment.

    - Filippo
  • mechan
    Anonymous said:
    @rcald2000

    I didn't want to reply directly to your question in case Filippo does answer you.

    Our CPU's are very similar. Most notable differences are 5820k(15mb L3 cache, 28PCIe lanes) and 4930k(12mb L3cache, 40 PCIe lanes). I know 1080's aren't Titan's but they're not that far off. My CPU has yet to go over 60% with both GPU's holding over 95% usage during 4k(60-80fps ultra, vsync on, AA min or off). It mostly averages 40%. This is with ROTTR, Witcher 3, GTA V, DOOM. The most obscene thing I've seen is how ROTTR loves to eat all the ram it can get, where ever it can get it.

    The firestrike physics tests nails it at 100% along with HD video conversions(including software using hardware accelerations).

    That being said. If you're really going all in for 2 of these then I would recommend seeing how your 5820 handles it. My personal experience in going from quads to hexes is that the lower hex speeds are more than compensated by the larger L caches and increased PCIe lanes vs a quad trying to hit 5ghz. I'm actually very surprised how many reviewers still obsess with using quads for these kinds of tests. Just look at the monsters in the 3d mark hall of fame and most are using 6,8,10 cores with their Titan SLI's.


    Increased PCIe lanes make absolutely zero (ok, maybe 1-2% at most) difference. Proof:
    http://www.tomshardware.com/reviews/graphics-performance-myths-debunked,3739-3.html

    The real difference is the clock speed and, to an extent, the cache size.

    The monsters in the OVERALL 3d mark hall of fame do indeed use 6,8,10 CPUs but, if you take out the CPU tests and look specifically at graphics scores the picture changes a lot.

    Anonymous said:
    @rcald2000

    When I put my old 970's from a 2600k(OC'd 4.20Ghz) to this 4930k(at the time 3.8ghz) I saw an average 10-20FPS increase in 4k. I was using the same memory and hard drives at the time.

    If people are going to try use a quad for 4k/5k 60+hz or 1440p 200hz Titan SLI or the mythical 1080tiSLI(January 2017?) then a quad will likely need to be at ~5ghz or higher(I'm thinking closer to 6). I'm pretty certain a hex or bigger will sit happy around 4-5ghz for this. Mine's at 4.10ghz because I still use all air cool options and I simply don't need more and its 24/7 stable.

    The other thing you may need to do if you take the leap. . .a bigger PSU. 850w can do it but a general recommendation I've heard for optimal PSU efficiency is to double the wattage you need. 2 Titan's and that CPU are going to push real close to 500-600 during a full load. I've watched mine at it averages in the 450-550 as is(but I've also got 2 raids and 3 or 4 other drives and that's including the display as well).


    The answer is actually simpler than that, as CPUs and GPUs follow Little's Law and Queuing Networks Theory. If his CPU utilization is at 50% with GPUs as the bottleneck, then the overclock he needs to shift the bottleneck to the CPU is precisely a 100% overclock (50%->100% utilization implies a doubling of the effective frequency, that is, a 100% overclock.) As mentioned in another response, that is simply not achievable under normal circumstances.
  • heliomphalodon
    I was keen to buy one of these, but I couldn't face the noise. I don't have the skills to mod a card for water cooling (not to mention voiding the warranty), so I went with a pair of Gigabyte 1080 water-cooled cards instead.
  • ledhead11
    Anonymous said:
    Anonymous said:
    @rcald2000

    I didn't want to reply directly to your question in case Filippo does answer you.

    Our CPU's are very similar. Most notable differences are 5820k(15mb L3 cache, 28PCIe lanes) and 4930k(12mb L3cache, 40 PCIe lanes). I know 1080's aren't Titan's but they're not that far off. My CPU has yet to go over 60% with both GPU's holding over 95% usage during 4k(60-80fps ultra, vsync on, AA min or off). It mostly averages 40%. This is with ROTTR, Witcher 3, GTA V, DOOM. The most obscene thing I've seen is how ROTTR loves to eat all the ram it can get, where ever it can get it.

    The firestrike physics tests nails it at 100% along with HD video conversions(including software using hardware accelerations).

    That being said. If you're really going all in for 2 of these then I would recommend seeing how your 5820 handles it. My personal experience in going from quads to hexes is that the lower hex speeds are more than compensated by the larger L caches and increased PCIe lanes vs a quad trying to hit 5ghz. I'm actually very surprised how many reviewers still obsess with using quads for these kinds of tests. Just look at the monsters in the 3d mark hall of fame and most are using 6,8,10 cores with their Titan SLI's.


    Increased PCIe lanes make absolutely zero (ok, maybe 1-2% at most) difference. Proof:
    http://www.tomshardware.com/reviews/graphics-performance-myths-debunked,3739-3.html

    The real difference is the clock speed and, to an extent, the cache size.

    The monsters in the OVERALL 3d mark hall of fame do indeed use 6,8,10 CPUs but, if you take out the CPU tests and look specifically at graphics scores the picture changes a lot.

    Anonymous said:
    @rcald2000

    When I put my old 970's from a 2600k(OC'd 4.20Ghz) to this 4930k(at the time 3.8ghz) I saw an average 10-20FPS increase in 4k. I was using the same memory and hard drives at the time.

    If people are going to try use a quad for 4k/5k 60+hz or 1440p 200hz Titan SLI or the mythical 1080tiSLI(January 2017?) then a quad will likely need to be at ~5ghz or higher(I'm thinking closer to 6). I'm pretty certain a hex or bigger will sit happy around 4-5ghz for this. Mine's at 4.10ghz because I still use all air cool options and I simply don't need more and its 24/7 stable.

    The other thing you may need to do if you take the leap. . .a bigger PSU. 850w can do it but a general recommendation I've heard for optimal PSU efficiency is to double the wattage you need. 2 Titan's and that CPU are going to push real close to 500-600 during a full load. I've watched mine at it averages in the 450-550 as is(but I've also got 2 raids and 3 or 4 other drives and that's including the display as well).


    The answer is actually simpler than that, as CPUs and GPUs follow Little's Law and Queuing Networks Theory. If his CPU utilization is at 50% with GPUs as the bottleneck, then the overclock he needs to shift the bottleneck to the CPU is precisely a 100% overclock (50%->100% utilization implies a doubling of the effective frequency, that is, a 100% overclock.) As mentioned in another response, that is simply not achievable under normal circumstances.


    In my case I'm pretty sure it was the cache sizes that made the most difference but I really did gain 10-20fps in going from my 2600k to 4930k. I also emphasize that the 4930k has yet to go over 60% in gaming with 1080sli while Filippo stated that the 6700k(4.2ghz) pegged 100% leaving the Titan's bottle-necked at 50%.

    I do completely agree with you on 144hz though. I honestly can't see much a difference from 110-144. I just mentioned it because of the new craze the display manufacturers are obsessing on and you know no matter how ridiculous there will be people trying to push it.
  • ledhead11
    In regards to the PCIe detail. I checked the link and as usual on Tom's, a good read. That's why your at the top of my bookmarks and one of the first things I read daily.

    Beyond that. I'd like to see the same tests done with the Titan X or 1080 SLI at 4k/5k/8k before really drawing a conclusion. Those 690's were awesome for the time but they don't really compare to today's needs. 1080p and 1440p don't seem to demand much but 4k/5k seems a lot more different.
  • ledhead11
    Anonymous said:
    +ledhead11 Thanks for the detailed response.

    ROTTR: I definitely have my eye on this game. One thing that I really respect is how the developer/publisher listed accurate recommended system specs. I also appreciate that they listed two specs: One for 1080p and the other for 1440p. I like titles that are highly optimized, yet push hardware to it's limits. How much RAM have you seen it consume?

    Your recommendation: It honestly didn't occur to me to wait and see how my i7-5820k handles the two GPUs before determining if an upgrade is warranted. I will definitely wait and see. I was also under the impression that a four core high clock rate CPU was a better match for dual high-end GPUs then a six core lower clock rate CPU. I hope that your conclusion is correct, because I really like the extreme processors and I'd like to continue using them.

    bigger PSU: Yes, the 50% of total available power is normally the most efficient part of the curve. Ideally a 1,000 watt Titanium (115V variant) would be a great option for two 250 watt PSU's in SLI with a top tier CPU. I've definitely considered upgrading to either an EVGA 1000 T2, or Seasonic Prime, although the later doesn't yet come in the 1,000 watt version. Honestly you will never recoup the cost of a titanium efficiency PSU over a gold efficiency; it's more of a pride thing.


    On both my setups I've seen it eat full Vram. The 970's at 1080p will hold 3.5-4GB. The 1080's will hold 8GB at 4k and sometimes drop a little at 1440p. Both running in Ultra, AA min, V-sync(1080p/4k) or G-sync(1440p). The system ram varies from 9GB up to ~12GB. The rig with the 970's only has 16gb and I find it shocking to see so much used at 1080p.

    Until this game I used to think 16/32 system ram was overkill for gaming. It obvious now that some games at 4k will need more than 16 on hand. I already knew 8gb vram was going to be an issue for present future 4k/5k but I couldn't really afford 2 Titans and I got tired of waiting for a TI. I'd been waiting since my 970's.

    BTW this is the only game I have that eats that much. GTA V is close but still not as much. Witcher 3/Doom are much more reserved in 4k with 3.5-6GB on average. In 1080p both just hang around 3-4 or sometimes less but not normally full on like ROTTR.

    I just remembered that I hadn't checked the numbers on my laptop(MSI GT80 2qe) which has 980m SLI(think a pair of 970s with lower than stock clocks and 8GB of Vram). Mines modified with 2 850's in raid 0 for games and 32GB/2133mhz ddr3 gskills like my desktop.

    For kicks, I maxed everything the game settings offer, AA included at 1080p. FPS dropped to 20-30. Test scene is the soviet union campsite at night with full snow(in my experiences one of the more demanding FPS renders, even more than some of the builtin benches). It used 11141MB System and 7282MB Vram. No exaggeration and this is 1080p/60hz. Tried Doom and vram was low like I said before but system was almost the same as ROTTR.
  • ledhead11
    Just saw this on 3dcenter.org and here's the link they had: https://www.facebook.com/hkepc/photos/a.10150610487158946.389221.94338753945/10154020385073946/?type=1&theater

    Kabylake 7700k I7 @ 6.7GHZ! could easily be fake but there you go.
  • nikoli707
    you would need to isolate which cores were bottlenecking in witcher 3@1440p to see if you need more cores all together or more clock speed per core to reduce the bottleneck. many are mentioning 6 or 8 core cpus, but i suspect the bottleneck lies with two cpu cores and not the need for multiple cores. im not saying that more cores clocked at an equal 4.2ghz wouldn't help, but is imagine a 7700k@5.2ghz would provide much less of a cpu bottleneck than a 6950k@4.4ghz.