Ideal CPU combination for GTX 1080Ti SLI or VEGA X-fire

[Fezlakk]

Hey everyone - long time, no post.

I am interested in a high-end, multi-GPU setup to power: 3840 x 1600 and 4K.

I am considering 1080Ti SLI or VEGA X-fire when it releases.

I want to avoid any sort of bottleneck, be it CPU or PCI.

The following review identified PCI bottlenecks, even with a considerably less powerful GTX 1070 SLI on 1151 versus 2011:
http://techbuyersguru.com/taking-4k-challenge-gtx-1070-sli-z170-and-x99 [/URL]

I have narrowed down three CPU combinations:

7700k
1700X; and
6850K

7700K gives the highest clocks and single threaded performance, but the 1151 chipset is limited to 8x 8x for SLI/X-fire; 1700x has more cores, but the lowest IPC, overclocking headroom, and is also limited to 8x 8x; 6850k is in the middle in terms of IPC, clock speed, and cores, and, crucially, has the capacity for 16x 16x multi-GPU - the only downside being that it is considerably more expensive

Which of these three would you suggest, and why?

Or should I just wait for intel to release X299, with hopefully cheaper access to 40 lanes in the wake of Ryzen?

Thanks!

 

[lehtv]

What kind of time frame are you looking at for the build? I'm guessing you're not in a hurry... It might be a good idea to just look at how the situation changes once software gets properly optimized for Ryzen and the full lineup of Ryzen CPU's is out. There could be cuts to Intel CPU prices.

Right now, i7-7700K is the "de facto" choice due to high performance per core. It will not be a limiting factor to fps at your resolution, for now. But longevity is a potential issue - with just four physical cores, when games become more demanding and you want even more graphics power, you'll have to upgrade. An overclocked 6-8 core will probably last 1-2 years longer. Another potential issue is multitasking... you're going to have problems doing anything CPU-intensive while simultaneously gaming.

I'd say it's the number of cores that determines what platform to go with. The number of PCIe lanes per card is a secondary issue, it will not make more than a few percent of difference. Maybe a 10% penalty at worst, usually about 5% - meanwhile, the second card improves performance by about 80% in games where SLI/CF works well. These are just guesses, however; I'm sure PCIe scaling will be tested shortly after the cards are released.

 

[Bouowmx]

Wait and see for how AMD Ryzen shapes up and Intel prices Skylake-X (X299).

PCI Express bandwidth is not an issue between 3.0 x8 and 16, although testing of multi-GPU setups is rarer than 1-GPU.
https://www.google.com/search?q=PCI+Express+bandwidth+and+multi-GPU

 

[Timmah!]

Go Ryzen - the IPC difference is negligible and i dont think there is any practical use to 16x lanes, 8x PCI-E is already plenty and does not hurt performance. At least i dont think it did with 1080, not sure about 1080Ti, but i would be surprised if this changed.

If you are hellbent on Intel, then 6850K over 7700K. Its mightily fine for all the games on the market and has the bonus of additional 2 cores for the future.

 

[tamz_msc]

First I'd wait to see how the GTX 1080Ti can overclock. If it is anything like the 980Ti, and given the fact that there are images of some beefy custom cards floating around, then one GTX 1080Ti might just be enough to drive 4K@60fps without compromising settings as much as the Titan XP.

 

[StinkyPinky]

Don't base your buying decision on 8x pci-e lanes as it has been proven time and time again there is no difference between 8 and 16x for gaming. 8x has enough bandwidth.

 

[Puffnstuff]

Or should I just wait for intel to release X299, with hopefully cheaper access to 40 lanes in the wake of Ryzen?

I believe that the release of x299 will force some market adjustments that might work in your favor regardless of what platform you ultimately choose. Socket 2066 will undoubtedly bring some performance enhancements that will force price drops and by waiting you will be able to take advantage of them. Personally I am excited over it and want to build a monster machine based upon it.

 

[Bouowmx]

First I'd wait to see how the GTX 1080Ti can overclock. If it is anything like the 980Ti, and given the fact that there are images of some beefy custom cards floating around, then one GTX 1080Ti might just be enough to drive 4K@60fps without compromising settings as much as the Titan XP.

So far, Nvidia Pascal all pretty much overclock about the same: 2.0-2.1 GHz; I don't see GeForce GTX 1080 Ti being any different. Keeping all else equal, perhaps the 8 fewer ROPs will make the GeForce GTX 1080 Ti perform a smidgen worse.

 

[guskline]

Ferzzlak, We have absolutely no public released information on Vega to make an intelligent decision. I am running 2 RX480s in CF on an Asus Prime B350 Plus mb with a R7-1800x and though the second RX480 is knocked down to 4x on the second PCIe slot due to the limitations of the B350 chipset (and that I can't find an X370 chipset mb in stock), your premise is based upon guesswork at present as to Vega.

 

[USER8000]

If you are spending that sort of money,I would wait a few more months for Vega and X299. It will also give a few more months for AM4 to mature and also for Ryzen to get better support.

 

[nathanddrews]

How long do you want this rig to last? I ask only because the limiting factor will eventually be the 7700K. Right now, 4C/8T is enough for many games and it's hard to argue with a 5GHz OC, but it is unlikely that there is any decent CPU upgrade path from the 7700K should you need more speed or more cores later. My information may be outdated, but I haven't heard one way or another if Intel is reusing LGA1151 for Cannon Lake.

Since you're not in a hurry, it won't hurt to wait for Vega (July/August), Ryzen platform enhancements (March/April), and X299 (August/September) before making a big commitment.

If it were my money and I were really anxious to spend it, I would jump on a Ryzen 1700 OC to 3.9-4.1GHz and 1080Ti SLI. I would forego the 900fps for long-term multithreading support.

 

[Bouowmx]

How long do you want this rig to last? I ask only because the limiting factor will eventually be the 7700K. Right now, 4C/8T is enough for many games and it's hard to argue with a 5GHz OC, but it is unlikely that there is any decent CPU upgrade path from the 7700K should you need more speed or more cores later. My information may be outdated, but I haven't heard one way or another if Intel is reusing LGA1151 for Cannon Lake.

Since you're not in a hurry, it won't hurt to wait for Vega (July/August), Ryzen platform enhancements (March/April), and X299 (August/September) before making a big commitment.

If it were my money and I were really anxious to spend it, I would jump on a Ryzen 1700 OC to 3.9-4.1GHz and 1080Ti SLI. I would forego the 900fps for long-term multithreading support.

Outdated: yes.

Intel Cannon Lake 10 nm will be mobile-only; Coffee Lake 14 nm takes its place for mainstream desktop, coming 2017 H2, likely Q4.
So far, Intel socket H has changed only with "Tock", now "Architecture"; Coffee Lake is "Optimization". I predict Coffee Lake will retain socket H4 (LGA 1151). There is a poll asking this question: https://forums.anandtech.com/threads/coffelake-thread-rumors-and-specs.2500407/
If Intel 100 and 200 series chipsets are compatible with Coffee Lake, the upgrade path from Intel Core i7-7700K is Coffee Lake 6-core.

 

[nathanddrews]

Outdated: yes.

You really confirmed nothing, other than I mistakenly typed Cannon for Coffee.

It would benefit the OP to wait until we know what socket Coffee gets. Even if 1151 gets one more generation, we're basically telling the OP to buy a dead-end platform. As an Ivy Bridge owner, I know how much it sucks not having anywhere to go. If he goes Intel and is looking long-term, then it would be beneficial to wait for the next platform. That could be another pro under the AMD column - socket longevity with AM4 is likely to be much longer than anything Intel has.

 

[tamz_msc]

So far, Nvidia Pascal all pretty much overclock about the same: 2.0-2.1 GHz; I don't see GeForce GTX 1080 Ti being any different. Keeping all else equal, perhaps the 8 fewer ROPs will make the GeForce GTX 1080 Ti perform a smidgen worse.

I think you're talking about GPU-boost. You can still manually overclock the Titan X Pascal, though you're going to be limited by the stock cooling. Yields of GP102 have improved and with cards with custom VRMs and better cooling solutions can in theory overclock much better than the Titan X. A repeat of the 980Ti overclocking is possible.

ROPs won't make much of a difference - faster GDDR5X can compensate for reduced ROPs.

 

[ddogg]

Dang 1080Ti SLI, that is going to be a monster of a machine in games where SLI scales. I actually don't suggest SLI because there are always small nagging issues and some games just don't support it. I currently have a 1080 SLI setup and just preordered a Ti to move back to a single GPU setup.

Sent from my Nexus 6P using Tapatalk

 

[ZGR]

Go for an r7 1700 and an X370 motherboard. No need to get a 1700x.

3840x1600 is a waste of money when 3840x2160 is cheaper. If you need 21:9 but want 4k, you will have to wait awhile.

A single 1080 ti will be able to do 4k
60 at high settings easily (no anti aliasing). I think a second 1080 ti may be a waste of $$ for 4k60. If you wait for a 4k120 monitor, a second 1080 ti will be necessary.

A 1700 + 1080 ti build is a great combination.

 

[ddogg]

I wouldn't say it will do 4K/60 easily based on how the Titan XP performs but certainly achievable if you turn a setting or two down. AA is useless at 4k and grass settings are the next most demanding setting. Volta x80 is likely going to be the card that does 4k/60 with everything maxed out

Sent from my Nexus 6P using Tapatalk

 

[Valantar]

At the very least, I'd hold off until some reviews looking into CF/SLI scaling on Ryzen get here. A month or two won't hurt.

 

[ZGR]

I wouldn't say it will do 4K/60 easily based on how the Titan XP performs but certainly achievable if you turn a setting or two down. AA is useless at 4k and grass settings are the next most demanding setting. Volta x80 is likely going to be the card that does 4k/60 with everything maxed out

Sent from my Nexus 6P using Tapatalk

I hate to be pedantic but aliasing is still easily visible at 4k unfortuately; unless you play on a 14" screen or below. 4x aa is needed if you want proper anti aliasing. Sadly, no GPU can do 4x aa at 2160p unless it is an older title. Aliasing is harder to notice, but the shimmering effect on power lines and thin objects is still easily visible unless you raise AA.

Since I play 2160p on a single 1070, I only utilize SMAA or no AA on newer titles. Aliasing is a minor issue but is still easily noticeable. I also turn shadows to medium and turn off ambient occlusion.

4k60 at high settings is easily achievable with a single 1080 ti, but when I say that, I mean high, not ultra.

The big killers at 4k are ultra shadows and ultra ambient occlusion. Lowering those two down to high or just turning off AO will fix any performance issues.

 

[moonbogg]

1080ti is coming out in a few days. You only have one choice and that's X99 with a 6850K or better. The 6800K would probably do nearly as well, but you'll be limited on PCI-lanes and you don't want that with two 1080ti's or faster GPU's. Wait for Skylake for the best possible choice, but that's 5 months away. Your minimums will suffer pretty nasty with a Ryzen chip with all that GPU headroom.
Also, I wouldn't go with a 7700K at this point either. Yeah its faster, but only 8x per GPU and those 4 cores are starting to stress out in some newer games. Won't be too long before it starts to choke. 6 cores/12 threads is a safe bet.

 

[ddogg]

I play on a 4k 32" screen and the difference is very negligible to me. Yes, I notice some jaggies with no AA but it's more like 2x MSAA at 1080p. The performance hit to have AA and the benefits you get makes it pointless to me.

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[Fezlakk]

Thanks, everyone - a lot of mixed responses to be sure.

I will definitely wait a few months - I want to see how big vega turns out: I doubt it will beat the 1080ti when both are overclocked, but if it is priced significantly less and is within 10 - 15% I might be game - especially considering the amount of Freesync monitors compared to G-sync.

At the moment though I'm veering towards the 6850K: yes, it's more expensive, but I think we are nearing the time when four cores just aren't enough; likewise for 8x. It would give me peace of mind knowing I have bandwidth to spare for the future, as I plan to keep this rig for at least two years.

I am really keen for someone to benchmark all three CPU's with 1080Ti SLI, or, at least, 6850k (or 6900k) versus Ryzen.

Thanks again.

 

[imported_jjj]

Will point out 2 key things.
1. With dual card there is some overhead and you want more cores- what games you play is always a factor since some scale to more cores, some don't but future games must scale to find more CPU resources.
2. Wait for Vega to see if the cache controller brings better scaling with dual cards.

 

[Kenmitch]

No real data on Vega so it's too early to decide. No info known about how Ryzen and Vega play together vs Vega and Intel....Who knows they could be designed to enhance each others performance?

 

[Bouowmx]

One Nvidia GeForce GTX 1080 Ti review features SLI: https://forums.anandtech.com/thread...han-titan-x-699.2500431/page-12#post-38784668