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This is something that has always bugged me - when I install a card into a desktop (ie mini tower) case, the fan is always facing down. Surely, making the card so the components and fan is on the top would help a lot with cooling, allowing those whiney fans to spin a little slower.

I know some card manufacturers tried to mitigate this by adding heat pipes and big heatsinks on the back of the card.. but they still put the bits on the same way as everyone else!

So, does anyone know why they're all upside-down?

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Flip the case upside down (ditto the optical drives). Voilá, no more upside down graphics card :) P.S.: not all are upside down, many Dell computers feature the motherboard on the left hand side of the case, the result: no upside down graphics card. –  Molly7244 Feb 21 '10 at 0:08
    
They aren't upside down in BTX cases, from the hot-running Pentium 4 era. –  paradroid Mar 27 at 7:09

4 Answers 4

up vote 15 down vote accepted

PCI (and PCI-Express) were designed to fit into cases that also contained ISA cards, but still use the same brackets. This lead to them being create with the opposite handedness.

I.e. the answer is historical reasons.

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More specifically, most or all of the early motherboards with both ISA and PCI slots were laid out such that both types of slots occupied the same space for a single bracket on the back of the case. This way, you didn't have to worry about whether a motherboard had enough ISA slots or PCI slots to accommodate the cards you wanted to install--you only needed to know if it had enough total expansion slots, in any assortment. –  rob Apr 28 '10 at 18:44
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But, to take up this thread again, WHY arent the PCI cards designed with the CPU on the back then? I know the SLOT design of the motherboards is historical, but that shouldnt keep the manufacteurs from moving the CPU/fan to the back of the boards? –  BerggreenDK Apr 10 '11 at 15:03
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@BerggreenDK The current arrangement keeps most cards within the space defined by the bracket. Putting components on the other side will interferer with the space for the next card. This hasn't stopped GFX cards from doing this (wrap around cooling mechanisms) when power consumption demanded it. –  Richard Jun 7 '11 at 8:50

It is my understanding that usually it's because the CPU is above the slots, so they are trying to keep the heat-producing components as separated as possible.

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To add what everyone else is saying -- hot air rises; you want the coldest air in the case flowing into your video card. And that air is the air at the bottom of the case, away from the CPU. This is why the fan faces downward. HTH!

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I'm not convinced - the coldest air is sucked in the front and then upwards to the exhaust fan next to the CPU. So the bottom of the case at the back doesn't really get good airflow. Especially when there a large PCB trapping it –  gbjbaanb May 9 '10 at 23:28
  1. you can buy inverted cases that flip the cards.
  2. It is true that the coolest air comes into the bottom of the case, and a downward-facing fan could take advantage of that air, however i'm not sure this is a REASON for this design so much as a circumstantial benefit.
  3. Having GPU below CPU keeps the GPU from getting more heat from the CPU, inverted boards/cases (mentioned above) are dumb unless you're more concerned about CPU temps than GPU temps, which you shouldn't be.
  4. The alignment of the bays in the CPU is such that the space granted for a slot lies beneath it on the rear panel, so it is necessary to put the components (including the cooling fan) beneath, simply because of the historical design of PCI/VGA slots. Why THEY had THEIR components (transistors, etc.) facing downard is a mystery, as this design does trap warm air generated by the components, however heat was a non-issue with most early computers using these slots. Enthusiasts didn't come along until well after the slot design had been established.

So if you REEEEALLY want your fans facing up, buy an inverted case with board on the left...but this will put your GPU above your CPU with any normal mobo layout so air management is important to ensure your GPU fans get cool air.

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