PCI-e x16 25 Watt Maximum?

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Ficisism

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Jan 1, 2014
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Hi. I have a HP Compaq 6005 Small Form Factor PC, and according to HP's manuals there is a 25 watt limit on the PCI-e slot (which is also a low profile slot). I got a HD 4850 and I would like to install it (I am aware that the card would not fit; I would have the side panel off to allow it to fit), but I don't think it would work with the 25 watt limit. My question is whether the 25 watt limit is actually enforced, because I've read that it means 25 watt limit on startup and then I've read that it is in place on the low profile slot. If it is enforced, is there any way around it? Otherwise I would have to buy a new motherboard and all to get it to work or buy a not-as-powerful low profile card. By the way, I have a 450 watt PSU (from Antec), so I believe that would be sufficient otherwise. Thanks.

http://h18000.www1.hp.com/products/quickspecs/13412_na/13412_na.PDF On page 17 under the PCI Express x16 listing it says 25W max power.

Unfortunately I am not aware what the motherboard is and I currently have no way to check (I haven't found any information online and I can't physically check).

TL;DR: I have a HP Compaq 6005 SFF and want to install a HD 4850 (with the side casing off the PC for it to fit), but there apparently is a 25 watt max on the low profile PCI-e slot. Is this actually enforced and is there any way around it?
 
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goodguy713

goodguy713

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ok well the 25 watt limit would have been for the internal psu and technically im pretty sure pci 2.0 has a 75watt limit so it might be because of the available power remaining on the power supply. That would be a guess how ever the 450 watt may be enough for that but only thing you can do is try you just need to make sure you either use molex adapters to power the card because you wont get enough power from the slot its self the power supply should have a couple cables just for a video card.
 
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Ficisism

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That sounds good; would the molex adapters connect to the card itself or to a slot on the motherboard? There is one for the 20+4 pin for the mobo, one for the PCI-E slot and an 8-pin that connects to the gpu?
 
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Pinhedd

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4x and 16x PCIe slots are limited to 25 watts of power delivery from the socket by default. Only full height GPUs with a 16x connector are allowed to configure themselves to draw 75 watts. However, there is no such thing as a "low profile PCIe slot", there are only low profile PCIe cards that have a thinner profile and shorter back-panel connector.

My guess is that the 25 watt limit is not enforced through any sort of hardware and was written with the stock power supply in mind, so you're probably in the clear.
 
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Ficisism

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Hmm... so you're saying HP put the 25 watt limit in the specifications as a sort of protection because the SFF casing limited itself to a low profile card? Sounds plausible. I didn't know that low profile slots did not actually exist and were determined by the card itself. Thanks.
 
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Pinhedd

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Yeah that's most likely the case. The standard does not allow a low profile card to draw more than 25 watts, and neither the case nor the stock PSU allow for a full height card.
 
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