Does PCI and AGP have a BIG design fault

starsky · Post by **starsky** » Mon Jan 06, 2003 10:46 pm

I just wanted to ask the question... in the hope that I am the only one analy retentive enough to ask the question...

Why are PCI and AGP cards designed with the chips facing down when in a tower case. Surely this means the heat on heat sinks is going back up into the chip?

Does this mean we have to run more, and faster fans to keep cards cool?

If the chips were on top rather than on bottom, surely we could remove the heat from the chip with lower powered fans.

Is there a reason I am not aware of they are designed this way?

Anyway my stupid though for the day while sitting in 40 degree celcius heat and my PC warming the room up.

Zyzzyx · Post by **Zyzzyx** » Mon Jan 06, 2003 10:59 pm

My guess would be that's just the way they were done when computer cases were still of the 'desktop' variety. Laid flat with the monitor usually set on top of them. And at that point in computer history heat generation wasn't really a problem.

I seem to remember seeing a case a bit ago that had the motherboard mounted on the opposite side, which then DID place the chips on the expansion/video cards on the top.

Zyzzyx
-pondering ideas for a mod

powergyoza · Post by **powergyoza** » Tue Jan 07, 2003 12:14 am

Zyzzyx wrote:I seem to remember seeing a case a bit ago that had the motherboard mounted on the opposite side, which then DID place the chips on the expansion/video cards on the top.

You're totally right. Any WTX case will have the mobo on the opposite side. This means the PCI cards face up. It also means the CPU(s) are below the cards (in the lower back of the case). If you go to http://www.wtx.org you'll find a PDF of the specs.

In the spec manual, I noticed some guidelines that could be important to us silentpc'ers. I've made a separate posting here in the fan and fan controls forum. Check it out here: http://forums.silentpcreview.com/forums ... =5677#5677

Beyonder · Post by **Beyonder** » Tue Jan 07, 2003 12:37 am

I have a chilli professional aluminum case that mounts the motherboard upside down. I love the layout of the case, to be honest - it seems really stupid to have everything going the other direction, if you ask me...

Gandalf · Post by **Gandalf** » Tue Jan 07, 2003 10:20 am

You're not the only one that wondered about this for a long time

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The thing that disturbs me the most however is the general stupidity of case-builders. I mean the first company that came up with a tower case must've been braindead or something. If they had designed the case to put the mobo upside down we'd be a lot better off today!

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Syphon869 · Post by **Syphon869** » Tue Jan 07, 2003 1:23 pm

Yes, peripheral cards need to be flipped, especially AGP cards. But flipping the whole motherboard is not the answer.

CPUs are at the top for a reason: heat. If the CPU is at the bottom, all that hot air is now travelling up and hitting everything else in your system.

The hotter the item, the higher it is in a standard tower case. PSU at the top, CPU below that, and then AGP slot under that.

Also keep in mind that Desktop systems were the norm before towers became popular, so that had alot to do with the placement of stuff on motherboards.

Personally, I'm not gonna worry about PCI cards, but the AGP card layout should definitely be inverted for the next slot revision. I also think they should add a second AGP slot.

Post by **Rusty075** » Tue Jan 07, 2003 1:33 pm

If you think it's bad in a regular tower imagine how it is to put a graphics card on an AGP riser card in a rack-mount. The card ends up being mounted with the GPU's heatsink and fan aimed right at the motherboard.

If only there was a way to invert it. Shouldn't be that hard really; All you need is a piece of PCB with the AGP pins on one edge and an AGP socket on the other, with the wiring traces crisscrossing each other as they cross the card. Obviously beyond a DIY project, but feasible.

Asmordean · Post by **Asmordean** » Tue Jan 07, 2003 8:05 pm

All that really needs flipped is the AGP card. I doubt many people have hot PCI cards. A sound or ethernet card isn't going to benfit from being the otherway around.

That being said, I wish a video card manufacturer would make a flipped card. It wouldn't be ATX complient, but so what. At least that little firebox on the card would be a little easier to cool.

quokked · Post by **quokked** » Tue Jan 07, 2003 9:51 pm

There are cases that mount the motherboard upside down to what most tower cases do, only problem is that the AGP slot is at the bottom of the stack and the CPU is below the AGP slot... I had one that had this type of setup, with the PSU covering half of the CPU, pain in the butt to work with, but if your PSU was a two fan one or had intakes in the right places u *might* be able to get rid of the CPU fan

Gandalf · Post by **Gandalf** » Wed Jan 08, 2003 9:07 am

Well I guess someone ought to design a case where the motherboard can be mounted upside down on the left side and the mobo people should invert their design so the CPU would at the current bottom and the future top of the thing! I don't care whether my AGP is at the bottom of the stack, actually that would be better cuz it's a bit colder there

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ez2remember · Post by **ez2remember** » Wed Jan 08, 2003 5:53 pm

This is a very good point, I go on to say the AGP card is in the wrong place too. Having two heat generators so close to each other makes it harder to cool and also causes hot air to be reflected/trapped around the AGP card, CPU and the PS. We all know having more breathing room would be better for cooling. Stick a tight bag around your head seal it around your neck and see what I mean, now get a large bin bag and do the same, there is a big difference in heat. Your components got to breath in this way too. Don't do it, just take my word for it, I don't want you to sufficate.

If the AGP card was near the bottom of the case which is generally cooler than the top, this helps cooling in itself, and secondly would be easier to cool since its not near another heat generator (lots of breathing room). Yes heat rises, but if your card is being cooled well, not much heat will rise from it. Heat will rise directly upwards hitting other PCI cards in the way, PCI cards don't cause much heat anyway, CPU/GPU/PSU/HDD causes tons of heat. The CPU would also run cooler with more breathing room.

I am a project to remove the PS unit from inside the case and building a fairly long external box for the PS. I may even add a intake panaflo fan @ 5v. This will be suspended or held in position with foam. A exhaust fan will take over its place from where the PS is currently.

The PS will only have to cool itself this way, without sucking all that hot air that is generated. My current exhaust fan will be inverted to become a intake fan blowing cold air directly over my heat sink / graphics. As hot air rises the exhaust fan will take it out at the top. There is more breathing room too. Lets hope this works, I will keep you posted.

Belgarion · Post by **Belgarion** » Wed Jan 08, 2003 7:43 pm

Asmordean wrote:All that really needs flipped is the AGP card. I doubt many people have hot PCI cards. A sound or ethernet card isn't going to benfit from being the otherway around.

That being said, I wish a video card manufacturer would make a flipped card. It wouldn't be ATX complient, but so what. At least that little firebox on the card would be a little easier to cool.

What about devices like the Zalman ZM50-HP or ZM80A-HP? With the heat pipes they use, a lot of the heat should be channeled from the "bottom" (in a standard ATX tower design) to the "top" side, on the back of the card.

Thinking about the start of this topic, I wonder if having the chips on the top side would really matter much, assuming the case already has good airflow. If you're really going for passive cooling and are relying on convection air flow, then every little design feature helps. But with a Zalman-style fan bracket holding a fan blowing over a heat sink on your VGA chip, would it really matter which side of the card the chip is on? The hot air coming off the heat sink would still get blown around until it's picked up by either the PSU fan or a case (exhaust) fan.

Tore · Post by **Tore** » Thu Jan 16, 2003 12:27 pm

I don't think the desktop cases have anything to do with the design of the PCI cards. I had a 486 in a tower case, and both the ISA and the EISA cards had the components at the upper side. Not sure about the VESA card, but I think it was like that as well.

So why did they change it for the PCI? Maybe because of the heat. If the heat is trapped under the card that make the heat, the card can be designed to remove the heat, but if the heat is trapped under the card above the card that produce it, the card above can't be expected to be designed to remove the heat. Just an idea...

Gandalf · Post by **Gandalf** » Thu Jan 16, 2003 12:31 pm

*opens up a bunch of 286's and 8088's*
You seem to be correct, most of my (E)ISA and VLB cards have their chips on the right/top side.
Honestly, I think that whoever came up with PCI/AGP slots simply didn't expect those cards to ever generate this much heat.

frodo · Post by **frodo** » Thu Jan 16, 2003 1:39 pm

If I remember properly the ISA and PCI cards also "faced" different directions. IE. the metal portion on the back of the card went different directions from each other. So looking at the top of a mobo your ISA cards were made so that the metal portion went to the right of the card and the PCI has the metal portion going to the left.

Obviously where the metal is there is more space so the chips were placed on that side of the card.

I believe they flipped it around for PCI cards so that people would not try to jam them into ISA slots. Thus we're stuck with chips that face down in a tower case.

I believe they left the AGP slot facing that way to keep its heat away from the heat of the CPU as a previous post mentioned.

Bat · Post by **Bat** » Thu Jan 16, 2003 2:39 pm

ISA and PCI facing opposite ways means that on motherboards that have both, there can be that "shared slot" where an ISA and PCI slot on the board share a single opening in the case. Perhaps that was the reason for the change of direction.

Note that in that new design for workstations (IWX?), the board has PCI slots with the components on the upper side. I agree that even weak fans will make convection all but irrelevant, though.

starsky · Post by **starsky** » Thu Jan 16, 2003 3:52 pm

OK,
from reading all of this I am convinced that the AGP is all we need to worry about. So who do we lobby to change Mobo design and the AGP standards to get t his changed. It surely can't hurt to try and change it. At least it is a logical argument.

crisspy · Post by **crisspy** » Fri Jan 17, 2003 10:09 am

Bat wrote:ISA and PCI facing opposite ways means that on motherboards that have both, there can be that "shared slot" where an ISA and PCI slot on the board share a single opening in the case.

frodo wrote:I believe they flipped it around for PCI cards so that people would not try to jam them into ISA slots.

Zyzzyx wrote:My guess would be that's just the way they were done when computer cases were still of the 'desktop' variety. Laid flat with the monitor usually set on top of them. And at that point in computer history heat generation wasn't really a problem.

Yup, that would sum it up nicely, except... the decision was actually based on a secret board room game of spin-the-bottle. Unfortunately, a bunch of other important things were also chosen that way... and are immortal standards to date.

In the days when these things were born, thermal design meant add more fans. And in a basic sense, they weren't too far off the mark. Heat has to get out of the box. Air takes it out of the box. Have more heat? Move more air, or your temperature goes up. Only case conduction can help out otherwise (ie. use other air that you don't have to move).

Heat does NOT flow up! It flows from warmer things to cooler things. That's called conduction. That's how heat gets from a heatsink into the cooler air that's touching it.
Heat does NOT flow up! Warmer gasses/liquids tend to be lighter than cooler ones, and therefore are displaced upwards by them (or outwards in centrifugal processes). That's called convection. It can help move air around, but it's a relatively weak contributor.
Heat does NOT flow up! A warm object/susbstance emits infra-red light, which shines away and possibly gets absorbed by other things, thus heating them up. That's called radiation. It's not that helpful to us with computers.

I think the real questions that needs to be asked are:
- How much conduction or air flow does a given component need to cool it?
- How do we get that much conduction or airflow.

The overall chimney effect of a vertical case certainly helps move air through it, and it seems like a good idea to have your overall case ventilation not work the other way. But I doubt that convection inside a computer case does very much in the big picture. Better to get a really quiet fan in there stirring things up a little, if the airflow through the case doesn't get everywhere that needs cooling. Or else find a different way to conduct the heat away from the components to much lager heatsinks, like the outside of the case (admittedly not easy). The Zalman AGP cooler is good because it creates a very high conduction path to a much larger heatsink area, where more heat can be conducted with less airflow.

As to which way up the AGP card goes? The GPU gives off lots of heat, so it needs lots of airflow to stay cool. Most quiet cases have a low total airflow, moving in the usual bottom-front-in through to upper-rear-out airflow scheme. An AGP card must tend to partition airflow inside a case, possibly creating an area with low total air exchange on the side facing away from the CPU. So I think it would help to have the GPU on the side facing the CPU because it is (hopefully) a better flowing airspace. Otherwise, Mike's often heard suggestion of using a very quiet fan to push some air through the usual GPU space (and past a really good heatsink) seems like a smart idea.

Lots of industrial equipment uses an air tunnel design. Anything that needs cooling is put in that space where air is made to flow, using fans or convection, by design, not by happy accident. The designers of PC form factors seem to have had other things in mind.

Ducky · Post by **Ducky** » Fri Jan 17, 2003 8:58 pm

I think it's the fault of the graphics card designers, actually. After all, the "high performance" cards tends to abuse the specs and just barely avoid bumping against the case cover in ATX cases...

In my case, for example... comparing the size of my old Voodoo 3 2000 card and my new NVidia card, it's easy to see why it's so easy for heat to be "trapped" underneath it.

In fact, I kept having graphics card lock-ups in my tower case until I bought a slot fan to keep the air moving underneath the card. (I had a fan in the front of the case originally, but that just made the air circulate somewhat, with no real way to escape, since I had wires running all over inside -- the resonance also made it sound like a jet engine.)

So, anyways... perhaps it's time for people to demand smaller graphics cards instead of more powerful ones?

Does PCI and AGP have a BIG design fault

Does PCI and AGP have a BIG design fault

The next question is who to lobby...