Watt limit on my PCIe?

DavidVioMC

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I was cleaning my PC out today when I noticed that it said 35W next to my PCIe port. I have no idea if my PC has a watt limit on my PCI or what, it's Dell Optiplex 960 SFF, it comes with 235W PSU stock so I though maybe Dell wrote that incase someone wants to put a GPU in with stock PSU and it warns users that you can only put a 35W GPU in on stock PSU. The current GPU I have is a GT 610 1GB and the max power output is 29W so I can't really test it with that, I have never seen a power limit on PCIe that's why I'm curious since I wan't to put a 750Ti in it.
 

COLGeek

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See here for more info on PCI-E power use/capabilities:

https://en.wikipedia.org/wiki/PCI_Express

Or read this excerpt.

Power
8-pin (left) and 6-pin (right) power connectors used on PCI Express cards

All sizes of ×4 and ×8 PCI Express cards are allowed a maximum power consumption of 25 W. All ×1 cards are initially 10 W; full-height cards may configure themselves as 'high-power' to reach 25 W, while half-height ×1 cards are fixed at 10 W. All sizes of ×16 cards are initially 25 W; like ×1 cards, half-height cards are limited to this number while full-height cards may increase their power after configuration. They can use up to 75 W (3.3 V×3 A + 12 V×5.5 A), though the specification demands that the higher-power configuration be used for graphics cards only, while cards of other purposes are to remain at 25 W.[12][13]

Optional connectors add 75 W (6-pin) or 150 W (8-pin) power for up to 300 W total (2×75 W + 1×150 W). Some cards are using two 8-pin connectors, but this has not been standardized yet, therefore such cards must not carry the official PCI Express logo. This configuration would allow 375 W total (1×75 W + 2×150 W) and will likely be standardized by PCI-SIG with the PCI Express 4.0 standard. The 8-pin PCI Express connector could be mistaken with the EPS12V connector, which is mainly used for powering SMP and multi-core systems.
 

COLGeek

Cybernaut
Moderator
See here for more info on PCI-E power use/capabilities:

https://en.wikipedia.org/wiki/PCI_Express

Or read this excerpt.

Power
8-pin (left) and 6-pin (right) power connectors used on PCI Express cards

All sizes of ×4 and ×8 PCI Express cards are allowed a maximum power consumption of 25 W. All ×1 cards are initially 10 W; full-height cards may configure themselves as 'high-power' to reach 25 W, while half-height ×1 cards are fixed at 10 W. All sizes of ×16 cards are initially 25 W; like ×1 cards, half-height cards are limited to this number while full-height cards may increase their power after configuration. They can use up to 75 W (3.3 V×3 A + 12 V×5.5 A), though the specification demands that the higher-power configuration be used for graphics cards only, while cards of other purposes are to remain at 25 W.[12][13]

Optional connectors add 75 W (6-pin) or 150 W (8-pin) power for up to 300 W total (2×75 W + 1×150 W). Some cards are using two 8-pin connectors, but this has not been standardized yet, therefore such cards must not carry the official PCI Express logo. This configuration would allow 375 W total (1×75 W + 2×150 W) and will likely be standardized by PCI-SIG with the PCI Express 4.0 standard. The 8-pin PCI Express connector could be mistaken with the EPS12V connector, which is mainly used for powering SMP and multi-core systems.
 

COLGeek

Cybernaut
Moderator
Given the 235w PSU, even the power sipping 750ti may be too much for this Dell SFF system. Does your particular 750ti have an external power connection?

This very well could be limitation (the 35w indicator) of this particular config, however, with a larger capacity PSU you might be okay. Those SFF systems weren't really designed for higher power (and heat generated) devices.
 

DavidVioMC

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The Dell OptiPlex has a custom motherboard power connector, so I need a adapater which I found one and I'm planning to put in a 500W PSU, I'm mosr censored about if the motherboard has some sort of watt limit on the PCIe or if Dell just put that sign incase someone wants to put a GPU higher than 35W on stock 235W psu.

 

COLGeek

Cybernaut
Moderator
Dell does often implement proprietary solutions in their devices. In this case, with a more capable PSU and a PSU to PCIe power connector (on the GPU itself), I suspect you'll be fine using the 750ti.
 

junkeymonkey

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adding a higher psu will not change the fact its a 35w slot that stays the same and a proprietary motherboard thing .

''some models of store bought computers [dell.hp,acer,ect..] may come with a ''locked or fixed'' bios and may not allow you to change certain hardware as a video card.. this is done to protect them from undue warranty claims and refunds .this is not done to hurt you but to protect them. you really need to see if that upgrade has been proven to work in your model first before you invest money in it .. there are a lot of these threads here at toms to look at some models will allow upgrades and some dont.. and a lot of guys here say ya ya ya when is really no no no...it would be sad you spent $200 on a card that wount post after you installed it as most find out. then get told its your psu and you spend more and end up right back where you are now, but its up to you good luck..


you got to know the the boards in these computers are not like the ones we use to do custom builds witch are open to upgrading with in the boards compatibly . the bios is custom made for there design and just for the parts they authorize to be used on there computers there only guaranteed to work as is out of the box as you bought it ,..


also these boards do not have to meet atx standards and there pci-e slot power may not do the required 75w needed for most higher end cards and can be limited to say 45 or 60w that is all thats needed with the low end factory oem cards that it may of shipped with ''
 

DavidVioMC

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So if it has a limited watt supply, it could be avoided with BIOS? Since it has to be programmed inside BIOS?
 

DavidVioMC

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I spend last 3 hours of doing research and I found this review on a MSI GTX 750Ti sale on Amazon, the guy talks about how he cut plastic on the heatsink ect to make it fit, I know exactly what he is talking about because after mesauring my PC GPU space, I also concluded that it will not fit and that's why I have looked into a PCIe riser card. This is what the guy said:
"After researching all the available Nvidia GPUs out there, this was the most powerful available in a low-profile short card format that would fit in a Dell SFF. Depending on the space available in your computer, this video card can be made to fit but you may have to modify it and the computer itself.

I have it currently installed Inside a Dell Optiplex 960 but needed to make two small notches in the plastic fan cover and heat sink to clear a capacitor and the Ethernet connector on the motherboard. This required using a Dremel and some trial and error to avoid cutting away more than necessary. In the end it was a perfect fit with less than 1 sq inch of area removed from just one of the dozen horizontal heat sink fins.

The next obstacle was the hard drive caddy which interfered with the video card's fans and cover. Fortunately the SFF I am using is already outfitted with a 2.5" SSD which is light weight and doesn't need the full caddy space for a 3.5" drive. Using the Dremel again, a narrow portion of the caddy was removed along the edge that needed clearance for the video card fans. The old 2.5" to 3.5" adapter was removed and the 2.5" SSD was mounted directly to the caddy with double sided foam tape. Given how light the SSD is, I am not worried about the foam tape losing grip and having the SSD fall on the motherboard.

One concern I often read about and also see mentioned is the required power supply wattage. Reading up on the GTX750Ti design and other GPUs, a majority of power is obtained from the +12V bus. Test reports show this GPU requires 64 watts on average but let's round that up to 72 watts. This only requires 72/12 = 6Amps from the power supply where the Optiplex 960 SFF spec claims 17Amps maximum on the +12V bus. Given the SSD is not power hungry with +12V, there is likely ample margin on powering the GTX750Ti even though the SFF power supply is stated as 235W max.

For those of you looking for the most powerful Nvidia GPU in this form factor, I would recommend this MSI N750TI-2GD5TLP graphics card."


He also provided this picture:

and it's excatly the same PC as me, now, the thing is, this is my second Optiplex 960 SFF, last one was tired as I used it for everything and dicided to get a new PC overall because it's cheaper to buy a whole PC that the moatherboard itself and I don't remeber having the 35W sign on it, so I'm not sure if it was only on selected PC's but after doing even more research, I couden't find 2 diffrent versions of BIOS it would require to create this limit.

 

scuzzycard

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Unfortunately, you can't believe everything you read here. I'm sorry that you were given bad advice, and I'm sorry that you had no way of knowing that it was bad advice. The issue is that the electronics on your motherboard were not designed to supply 65 watts, they were designed to supply 35 watts. It's not a PSU issue, and it's not a BIOS issue. It's not something you can fix or change.

I hope it works out for you.
 

DavidVioMC

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I tried to call/chat Dell about this but they're closed off for today, I'll try tomorrow, I just want to see what they have to say, I'll also give a call to my good friend who used to refurbish Optiplex 960 SFF into gaming/karaoke PC and he was the first person that sold my first Optiplex 960 SFF so maybe he also knows something about it.

 

scuzzycard

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I'll make it easy for you - anyone who tells you this is a good idea is wrong or just guessing, and anyone who tells you it's a bad idea is right :)

You don't know me from Adam, so I understand you not taking me at my word. Dell would not waste time printing that "35W" label on your motherboard just to josh you.
 

DavidVioMC

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I have seen people run 750Ti's in Optiplex 960 with my own eyes, but I never seen anyone run 750Ti in a 960 SFF. There are plenty threads out there about people asking for GPU's for their 960 SFF, but people have only suggested GPU's that will fit, and the only GPU's that will fit are GT 730 and lower and they require max 30W, so nobody was like "You can put in a GT 730, but hey, Dell lockd the PCIe to 35W." I have no idea if 960's and 960 SFF are very similar or if the 960 SFF motherboard is based of 960 motherboard. The only source that I could find is people installing 750Ti's inside 960 SFF, but there's no videos/pictures of them actually running. I found this guy leaving a review on Gigabyte 750Ti:
"Most powerful card for its size with extremely low power usage. Fit and works perfectly in my Dell Optiplex 990 SFF with no modding (i7 2600)"
That review was posted on 2016-05-24 so it wasen't that long ago, he said that for 990 SFF, it's not 960 SFF, but from my research, 990 SFF is based off 960 SFF and the only diffrence I can see if bigger psu, better stock cpu & gpu, nothing else. There is a video off a guy running a 750Ti in Optiplex 390
https://www.youtube.com/watch?v=W8lsQP2PzIU
There are small traces off people puttin in 750Ti's inside 960 SFF and even bigger about people putting 750 Ti's in Optiplex's overall, if Dell says they don't know or it's actually limited ect, then I will propably get something like 900 series GTX that requires a power connector and draw power from that, but I'm not sure if the GPU will put load on the PCIe by trying to pull 75W when the PCIe will not let it.

Shortly after writing this, this video peope up in my recommended list on youtube, it's a guy putting in a 750Ti inside a Optiplex 780
https://www.youtube.com/watch?v=WR83S2gYutM

 

DavidVioMC

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Dell just replied, they said, yes, indeed the 960 SFF has a limit of 35W in the PCI-E but they said a more watts GPU might work but for few customers it was a no luck and for few it worked like a charm.

This is why some people did end up puttin in a GPU like 750Ti because it may have worked for them, and for some it may not, but I have only seen good reviews, such as "it worked on my 960 SFF" but I haven't seen anyone post "It didn't work for me", so I would guess, there's a higher chance of getting it working? Not sure.

Asked them again by how many watts I can risk it without frying anything, I'm expecting and answer of 10 but let's see.

 

killrose

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I am dealing with a Dell 1070 that crashes when running my R9 290 in benchmarks. I have taken the motherboard out of the case an put it into a med ATX case, because the motherboard on the OptiPlex 1070 is not a crappy BTX style board. Long story short I have to UNDERclock my video card from 1050MHz to 850MHz to get it to pass Firestrike benchmark. I am running a CX650 Corsair PSU.

Now I can run the same card in the same case fully overclocked 1050MHz gpu / 1300MHz mem all day long gaming, BUT with an OptiPlex 990 motherboard instead of the 1070 motherboard. I tried to go to the 1070 because it has Ivy Bridge support and uses the Q77 chipset, the 990 uses the Q67 chipset. But evidently, the PCI-e slot spec is 35watts (or less) on the 1070 and even though I have a 6-pin and an 8-pin on the R9 290 the combined power needed is not quite enough for my power hungry card.

If you can boot into desktop and lower clocks you may find you have something workable, just not at max clocks
 

scuzzycard

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I will add this in, just in case someone is feeling adventurous - any Maxwell card can be configured to draw a specific maximum wattage from the Slot as long as it has a separate 6-pin or 8-pin from the PSU by using MaxwellBiosTweaker. The wattage limits can be set for each rail independently. Unfortunately, I can't give lessons on how to use the program, but if you're so inclined, feel free to do the research.
 

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