Power supply for Titan Xp

Hi,
I recently purchased a Titan Xp which requires a 6-pin and a 8-pin connectors but I have only two 6-pin connectors. Will an adapter work or what is the best way to go about it?

Buy a power supply with the proper connections and power rating. It will cost a lot less than your Titan Xp.

Do not use 6-pin to 8-pin converters or Y-splitters in the PCIe power cables to the GPU. Doing so is asking for trouble. Size your power supply wattage so that the sum of specified wattage of all system components is in the 50%-60% range of it. If the Titan XP is your only GPU, and if your system has a single CPU socket, that sum is likely 250W + 100W = 350W, calling for a 600W power supply (which is, not so coincidentally, what NVIDIA suggests: https://www.nvidia.com/en-us/geforce/products/10series/titan-xp/)

I would strongly recommend an 80 PLUS Platinum rated PSU. They are more efficient and often more robust due to the use of higher quality components. They have become quite affordable, and if you plan to use your GPU heavily you’ll likely get the additional cost back in a year due to lower electricity costs.

I am making these recommendations based on experience with all the things I tell people to avoid. 6-pin connectors are designed to deliver 75W, and are connected accordingly inside a PSU. 8-pin connectors are designed to deliver 150W, and are likewise connected accordingly inside the PSU.

Thanks njuffa for your response, I probably should have been more specific.

My workstation is a Intel Z440 and it has a PSU which is 80 PLUS rated but supports 225W for graphics power supply with two 6-pic connectors. Here is the detail about the PSU I have:

HIGH-END
700 watts wide-ranging, active Power Factor Correction, 90% Efficient, with two graphics power cables
700w PSU will support up to 225w of graphics
The Z440 700W power supply efficiency report can be found at this link:
http://www.plugloadsolutions.com/psu_reports/HEWLETT%20PACKARD_719795-001_700W_ECOS%203915_Report.pdf

Now the NVIDIA website for TITAN XP mentions that the power consumption of the GPU is 250W but I do not understand how this will work even with the 6-pin and 8-pin configuration (75 + 150 = 225W).

To be safe and to allow for two GPUs (one compute one for video) you should have at a 80 plus power supply with at least 1000 watts. I typically get a 1200 W or 1300 W for a 2 GPU system.

Power Supplies are one of the workstation components which are most likely to fail over time so it makes sense to spend the extra $100 on a top line version.

I only have 1 GPU (Titan Xp) for video and compute.

The slot itself provides up to 75W as well. 75W(6-pin) + 150W(8-pin) + 75W(slot) = 300W max, for a graphics card that has a 6pin and an 8pin requirement.

So 225W is definitely underpowered for a graphics card that may consume up to 250W. But if you are judging that strictly from the 6-pin and 8-pin connectors, then your judgement is off as well, since some of the graphics (slot) power comes from the PSU connectors feeding the motherboard.

However, a 700W PSU may be somewhat borderline for a 250W GPU, and in order to convert 6-pin to 8-pin connectors, to do it correctly requires a dual 6-pin to 8-pin dongle. These do exist if you look for them, but I would recommend (again) that you just get a PSU that is up to the task. The $100 cost or so is quite a bit less than the cost of your Titan.

The part you are missing is that the PCIe specification states that the PCIe slot itself can supply up to 75W. As far as I know, NVIDIA GPUs typically only draw 50W-60W through the PCIe connector, i.e. well within this specification. A PCIe-compliant GPU with a 6-pin plus an 8-pin connector can draw up to (75W + 75W + 150W) = 300W.

Note that power ratings for computing devices of any kind typically do no account for very short-term spikes in power draw. The 250W specified for the Titan XP therefore is maximum power draw averaged over a reasonable time interval, let’s say 10 seconds (I do not know what time interval is actually used when these numbers are defined). This applies similarly to other system components and is one reason that you would want to use only 50% to 60% of a PSU’s rated power output (another reason is poor efficiency and increased thermal load leading to shorter component life span when exceeding that range).

As I said, if the PSU offers a 6-pin power connector the cable is connected inside the transformer such that it can reliably supply 75W, plus maybe a 20% engineering margin. For a 250W Titan XP, if 60W come from the PCIe slot, and another 75W from a six pin connector, that leaves 115W to be supplied via the 8-pin connector, which exceeds what can be reliably delivered on the second 6-pin connector even when taking into account typical engineering margin.

Now, a GPU won’t draw 250W all the time, and you may get by with a 6-pin to 8-pin converter for quite some time, only to have the GPU malfunction (due to undervoltage) under high load, and likely at the most inopportune time, as Murphy’s Law dictates. That’s what I meant by “asking for trouble”.

As for 80 PLUS ratings, please note that there are different efficiency levels. From least to most efficient: Bronze, Silver, Gold, Platinum, Titanium. For smaller computers (workstation) I would recommend a Platinum rating, for larger computers (servers) I would recommend a Titanium rating. If you operate in an environment with low ambient temperatures and cheap electricity, dropping down one level is reasonable. I live in California where the climate is warm and electricity expensive. A useful overview of available 80 PLUS power supplies can be found here: https://plugloadsolutions.com/80PlusPowerSupplies.aspx.

It would help performance and not lock the screen if you put a cheap GPU for video out and keep the Titan Xp as the compute engine.

For example if you are training a DNN for a number of hours but still want to be able to work on other non-GPU items this allows no issues with either the Xorg (linux) or the WDDM (Windows) driver.

CudaaduC:
I have a spare GPU which can work for video but the slots are in weird positions, so after fitting the Titan I do not have room to put the secondary GPU as the SSD slot blocks it. Anyways that’s a different problem and please let’s not digress from the topic. I am trying to solve the power consumption problem in this thread.

Thanks for the advice txbob and njuffa. I guess I am led to believe that the PSU doc that says “with two graphics power cables 700w PSU will support up to 225w of graphics” can be in no way true…

What makes you think that? The fact that the PSU is rated for a total 700W across all available connectors has no bearing on the fact that the two 6-pin PCIe power cables it provides are limited to 75W (plus engineering margin) each. PSUs of identical power rating can be constructed in myriad different ways, depending on the use case they target.

You are of course free to proceed with the use of 6-pin to 8-pin converters, and if your GPU workloads never come close to the 250W limit of the card you may even enjoy long-term stability with this setup. But you should be aware of the risk.

The reason why I said that was because: If the 2 6-pin power cables are limited to 75W (plus margin) each, then how can they support 225W of graphics? That does not seem correct to me…

Two six-pin power cables @ 75W each + PCIe slot @ 75W = 75W + 75W +75W = 225W.

I see, it includes the PCIe slot as well…Thanks!

Is it possible to have a separate PSU to power only the GPU while the rest of the components on the motherboard draw power from the existing PSU or does everything including the GPU have to draw power from a single PSU?

It’s not a good idea. Electrically, if all components were isolated (only sharing a ground connection) then this would be possible. However the fact that the PCIE slot is inevitably powered from the motherboard PSU means that if you provide a separate PSU just to power the “aux power” connectors, then you have the possibility for rail-to-rail paths which can be bad.

If the circuit design of the PCIE card is carefully analyzed (for example, the PCIE bus itself is capacitor-coupled), then this condition can be ruled in or out. But without access to the design you are flying blind. And NVIDIA makes no claims of support in such a scenario, failures would not be covered by warranty.

Doesn’t a Titan cost in the vicinity of $1000? Doesn’t a PSU cost $200 or less?

This is being penny-wise and pound foolish. Buy a good PSU, if for no other reason than to protect that $1000 asset.

No need to make assumptions without knowing the full picture. Upgrading the PSU in the HPZ440 might not be an option and could potentially void the warranty on my workstation as well. Therefore I am thinking of alternative solutions. Thanks for your input.

If you are concerned about warranty, or if the existing PSU uses some non-standard connectors (!), I would suggest calling up the workstation vendor to find out whether they offer an alternative PSU for that machine. My experience is that they often utilize multiple PSU models with a particular machine, but ship the smallest variant that fits the configuration you specified when doing the original purchase.

You are probably aware that vendors that sell customizable workstations often add a hefty profit margin of their own to standard components such as DRAM or GPUs, and I would not expect that to be different if and when they offer alternative PSUs.

Sorry for coming here so late, but I just bought the Titan XP and tried to install it into my Dell XPS and realized it didn’t have a good enough power supply.

While my first thought is to return it (under nVidia’s 30 day return policy) I really want to use this card. Now, I’m an OLD man, and while I used to build computers that was so long ago I doubt whether most of you were still alive back then. I’m not uncomfortable with the prospect of changing out my power supply, it’s only that I’ve bought Dell computers for so long I’m not so sure how easy this would be.

So just in looking around I’m wondering if this particular power supply (assuming it fits my computer – that’s another issue) would work for the XP?

https://www.amazon.com/EVGA-SuperNOVA-Modular-Warranty-220-G2-0850-XR/dp/B0106RDIN2/ref=sr_1_6?ie=UTF8&qid=1517768206&sr=8-6&keywords=psu%2B80%2Bplus%2Bplatinum&th=1

If not, could anyone point me to one that might? I don’t mind spending a hundred or two more if I can use this card, but I don’t want to spend weeks trying to get this right (at my age time is worth more than money). I have four internal drives in this machine (so I’m using a lot of power cords) and just the one GPU. TIA for any words of wisdom.

A 650W power supply such as the one shown should be sufficient if the Titan XP is the only GPU in the system. Rule of thumb: Sum of nominal wattage of all system components should be <= 60% of nominal wattage of PSU. With four internal drives (~7W per HDD/SDD) you are probably close to that limit, but not over.

I suspect your biggest problem will be fit. I have taken the same trajectory as you have, in that I built many system myself in the past before I switched to buying machines from Dell for my personal use starting in 2003. From what I have seen, Dell (as well as HP) have a tendency to incorporate non-standard PSUs into their machines, e.g. either their dimensions or the power cable connectors for the motherboard are unusual.