Ultimate Build for Number Crunching with Wide Open Budget

[afalk42]

I am in the process of spec'ing out a new rig specifically with the dual purpose of being a high-end PC setup for gaming and VR, but also number-crunching for various GPU-intensive distributed computing projects (e.g. BOINC, rendering, crypto-currencies, PrimeGrid, etc.).

With the new Pascal-based GTX 1080 graphics card coming out at the end of this month, my goal is to build a rig with 4 (four!) GTX 1080 cards in it. At the moment my intended parts list looks like this, but imagine the 4 GTX 980Ti cards being replaced by 4 of the new GTX 1080 cards.

So here are my questions:

■ Will it even be possible to run 4-way SLI with four of the GTX 1080 cards? Or am I going to run into thermal issues and do I need to scale back and just buy 2 of the GTX 1080 cards? Has anybody run 4 of the GTX 980Ti cards before and what is the experience with heat dissipation, if the cards are that close together? I am planning on a big tower with plenty of fans, so should have ample cooling capacity, but am still worried about airflow with those card...
■ My primary displays will be the same 2 Samsung 4K monitors that I already own. What's the best way to connect them to the 4 GTX 1080 cards? Do I connect both monitors to the 1st card and use SLI connectors to connect all four cards together in a 4-way SLI configuration? Or is it better to have one screen on card 1 and the second screen on card 3, and connect 1+2 in a 2-way SLI as well as 3+4 in a 2-way SLI? Any experience from people with dual screens connected to graphics cards with 4-way SLI would be much appreciated.
■ For high-end distributed computing tasks I am a bit concerned that with just one Core-i7 CPU - even the 6700K at 4GHz - I could end up being CPU-limited with four of the new Pascal-based GPUs. Would it make more sense to go with a Xeon multi-core CPU in this case and take a motherboard that can accept 2 Xeon CPUs? There seems to be only a very small selection of those boards available, and none of them seemed to support 4-way SLI. Also, I'd really like to have a Skylake-based CPU, and thus the current planned parts list has the Core i7-6700K in it.
■ Any other comments and input on my planned parts list would also be appreciated.

 

[coozie7]

Given the VERY considerable outlay you're looking at here I'd be reluctant to advise you take advice just off the 'net. Don't get me wrong here, there are some very capable posters on this Forum, but I feel you'd also be well served by getting some professional advice as well as E-mailing the software vendors/publishers for their opinions on what hardware configuration will best serve your requirements.

My own drivel:

1: TBH I have no idea, I just don't move in this kind of circle, but what info that IS available strongly suggests the GTX1080 will use far less power than the current GTX980Ti so I'll just suggest you keep your eyes open for the reviews next month because cooling 4 GTX980Ti's is likely to force you into a massive liquid cooling loop (or loops).

2: Pass.

3: Again, check with the software people, but Xeons are better suited to maths type tasks than general purpose CPUs, depending on how the software can use resources it may be better to sale UP the CPU/s to dual Xeons and dial back the GPU/s.