This monster PC has four Nvidia RTX 3090 GPUs – and...

If you’ve dreamed of owning a PC with one of Nvidia’s RTX 3090 graphics cards embedded in it, how about a computer that has four of these GPUs on it?

Making workstation PCs for customers who need extremely powerful setups, Puget Systems experimented with the idea of ​​a single computer containing four RTX 3090 GPUs and wondered if that might make sense. And the short answer is, it does – with some caveats on the power front.

The rig put together by Puget (discovered by Videocardz) contains, as mentioned, four RTX 3090 graphics cards as well as an Intel Xeon W-2255 10-core processor with 128 GB of RAM (the full specification can be found here). The power supply came from an EVGA SuperNova 1600W P2 power supply unit.

Of course, this is a workstation PC geared toward heavyweight applications – it’s far from a gaming machine, and the PC maker tested it on benchmarks that included OctaneBench, V-Ray Next, RedShift, and DaVinci Resolve. With these pro apps, the user can use multiple GPUs without driver support (or they are connected by NVLink, which “only” supports two 3090 GPUs anyway).

The result was that the system performed admirably in these tests, with the performance of these GPUs scaling roughly proportionally as more RTX 3090s were added to the mix (up to the full four).

The exception was DaVinci Resolve, which scaled out to three GPUs, albeit with more modest improvements. However, the addition of a fourth RTX 3090 did next to nothing to improve performance (although this could be partly related to a CPU bottleneck – this 10-core Xeon was chosen to keep power consumption low on the processor front. RedShift also scaled up) not quite as good when moving to three or four graphics cards, but still saw a decent improvement.

Advantages of the blower

Puget’s RTX 3090 cards were Gigabyte’s 80mm fan models, the company stated, “This type of fan cooling system is much better for multiple GPU configurations because it gets most of the heat straight out of the back of the case gives. And when it comes to four 350 watt graphics cards, that’s 1,400 watts of heat that we want to get out of the system as quickly as possible. ”

You are not kidding. Either way, it turns out that this setup worked just fine from a thermal standpoint, with the GPUs running between 73 ° C on the bottom card and 80 ° C on the top board (with the 3090s hitting 88% of their maximum fan speed – what as you can imagine, made for a noisy pc, but that’s to be expected).

So the problem with this experimental Quad RTX 3090 PC wasn’t temperature or noise, but power consumption was a more delicate issue. The 1600W power supply was just about able to handle it, but it was a very close affair.

As Puget points out, a maximum power consumption of 1,717 W was measured from the wall socket, which should correspond to around 1580 W (the power supply with an efficiency of 92%) in the PC, which means that 20 W was left.

This is of course too close for comfort for constant daily operation. Therefore, Puget recommends using a 2400W power adapter. “Most home and office electrical outlets in the US operate on 15 amp circuits, which may mean hiring an electrician to do electrical work if you choose one of the few 2400 W power adapters available. ”

If you can afford this type of workstation PC and the pockets are deep enough for four RTX 3090s, the extra electrical work probably won’t be a major sticking point.

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