Multi-GPU Graphics Cards

[LonePalm]

I just ran across an article discussing upcoming graphics cards with more than one GPU on a single graphics card.

Why You Don’t Need Multiple Graphics Cards
http://www.rockpapershotgun.com/2015/02 ... od-or-bad/

Does anyone know anything about this and how it might affect folding?

[PS3EdOlkkola]

I have a good amount of experience using variations of dual GPUs on a single card for folding. I tend to set up my systems with an eye toward maximizing the available performance per available physical slot (also optimizing folding slots) in a given system and dual GPU cards can perform quite well in that design paradigm. I've used the Nvidia GTX 690 (two GTX 680's in one double-width PCIe form factor), the AMD HD 7990 (two HD 7970's) and the AMD R9-295X, which contains two R9-290's on a card. On Core17 work units, like a p13000, the GTX 690's do about 160,000 ppd on the 327.xx drivers, the HD 7990 does 270,000 PPD on 14.4 drivers, and the R9-295x performs at about 475,000 PPD on the 14.12 drivers. The practical performance advantage lasts about one GPU generation, where the next generation GPU architecture for the single GPU high-end card meets or eclipses slightly the performance of the last generation dual GPU card. By way of example, the GTX 690 provides about the same performance as a GTX 780 per physical slot. Likewise, the R9-290 provides about the same performance per physical slot as the HD 7990. If you tend to upgrade your GPU every two years, getting a new dual GPU card on the front-end of its initial availability gives you about two years worth of very good folding performance that provides about 2x PPD of that same generation GPU in a given physical slot.

The downside is you need to build your system with way more airflow than you'd need if you just put two separate GPUs in the same case. For the air-cooled solutions like the GTX 690 and the HD 7990, they're like little nuclear heaters when folding and need all the airflow they can get. It's possible with the reference design of these two cards to get water cooling blocks that manage the heat and help reduce fan noise, and I've done that with the HD 7990's (but they still can't overclock more than 5% to 8% and be stable, so a relatively bad investment!). The R9-295x comes with a factory-designed water cooling system, and simply adding an additional 120mm fan keeps the GPU temps in the mid-to-high 50 deg C range and the noise is very tolerable. I currently run six R9-295x GPUs and they've performed flawlessly for well over a year.

[bruce]

Dual GPUs are a niche market. Only if the top-of-the-line entry in the current generation of GPUs is not powerful enough for you, will you opt for running more than one GPU. Whether those GPUs are installed sharing a single board or your case has room for them to be in multiple slots is mostly a function of the physical space in your case.

The technology to split the video processing of generating a single image of your game on your screen is called SLI by nVidia and CFX by AMD. FAH doesn't need that technology and ignores it if it's configured. Instead, they manage each GPU separately whether they're a matched set or they're different GPU models.

[LonePalm]

Thanks to both of you for your very helpful answers.