High end PC heat issue

[Frank4d]

I am building a system at work which has the following (important to this discussion) specs:
4U Industrial rackmount chassis with 460 watt PSU
4 PCI-X + 8 PCI slot passive backplane
Dual Xeon CPUs @2.0GHz single board computer (SBC) @533MHz FSB with 4GB PC2100 DDR RAM
Matrox Imaging Odyssey XPRO (1GB) RGB video capture card
Matrox Imaging XG (256MB) video display card
Eight other PCI cards installed

The SBC installs in the backplane between the four PCI-X slots and eight PCI slots. All is cool over on the PCI side. On the PCI-X and SBC side, I have a potential heat issue to address. It may not even turn out to be a problem, but the hardware in this computer costs about $80,000 so I don't want to find a problem later.

The SBC is a full length PXI-X card installed toward the middle of the chassis. The heatsinks on the two CPUs are are about 2x3x3 and each has a 80mm fan. They are at the far (away from the back) end of the card and low air toward the back of the chassis.

The next slot in front of the SBC is taken by IDE, Floppy, COM, LPT, and USB port cables.

The next slot in front of the SBC contains the Matrox Imaging XG display card. It has a large finned heatsink (about 3x3x0.5) on top of the Oasis ASIC (graphics processor), with no fan.

The fourth PCI-X slot contains the Odyssey XPRO video capture card. It has two Motorola G4 processors each with heatsinks and fans (about 2x4x0.5). This card is about 1/2 inch from the left-side chassis wall.

At the far end (away from the back) are two 120mm fans blowing air across the cards. And not doing a very good job because there is so much stuff in the way.

The BIOS reports that the Dual Xeon CPUs are running 31-C and 34-C. When I run my hand over the cover of the chassis I detect a hot spot (feels like 50-C) which is about 4x4 inches and is centered about one inch above the Oasis ASIC on the video display card and two G-4 processors on the video capture card.

I can't move the cards to other slots, there is no room for water cooled, Peltier, or cold plate heatsinks... the cards are in adjacent slots. I am screwed there.

So my only option so far as I can see is to add fans. I have an area about 3.5x3.5x1 inch to add fans. Would it be better to blow cool air into the system above the hot area? Or exhaust air from above the hot area? And does anyone know of small fans that have really high air flow (screw the noise)?

 

[Budley]

The trick to air cooling your PC is to keep the air exchanged at as high a rate as possible without sounding like a jet taking off. Simple fan configuration would be one large one in the front pulling air in with another in the back to assist the PSU fan in pulling air out. Air flow will be from the front of the case to the back. A drastic mod that I've seen work well if the card crowding prevents good air flow is the installation of a fan on the cover facing the MB and positioned just above the cards themselves. Although this mod works well I don't like it for the simple fact that it makes removing the cover a hassle, but if it's the only option, then give it a try. Another option is installing a "blow hole" on top of the tower cases to pull more air out over the CPU and memory, (ATX MB configuration). This is usually the loudest option, but effective in assisting the heatsink on the CPU. As far as fans, I can only recommend doing some research on some of the mod forums. The OCing community is up on all the latest cooling technology and can recommend the best fans. Remember to clean up your cabling as much as possible when your mucking around inside. This can make a huge difference in cooling efficiency. Good luck.

 

[paparazi]

Budley
What you are describing is all well and good for a standard desktop ATX layout but Frank4d is building something quiet differant.
I do think however (as you pointed out)the best solution here (if possible) would be to cut a 92/120mm hole in the side cover, parallel to the hot areas, mount a fan and finger grille, blowing straight onto these expensive cards.
Obviously without seeing the case layout and cover contruction, I don't know if this is possible.
If this is possible, then you might need to take the cover to a local fabricators to make a clean hole.
A chrome fan grille fitted to the outside should leave it looking nice and neat and protect those fingers.
Martin


We like members to GIVE and not just TAKE.
Participate and help others.

 

[Frank4d]

The computer I am building is similar to this one:

http://users.adelphia.net/~frankford/Comp_small.jpg

It is approximately 18W X 7H X 29D. The cover is removed. There is a filtered air inlet that is about 9x7 inches on the front and there are three 150 mm fans blowing air toward the backplane. There are slotted vent holes on both sides and rear aboce the cards.

The problem heat area is about where the memory sticks are located. As you can see, there isn't room to add much of anything in that area... except I do have about one inch between the top ot the cards and the top cover.

I am thinking of mounting one fan under the cover that blows air down on to the CPU and graphics card hot chips. And then another fan 4-5 inches away (still above the same cards) to exhaust air. I will have to cut holes in the cover and put in some filtered grilles.

I'll see if I can post a better picture today.

 

[Crowley16]

the hotspot suggests that something is interupting the flow of air through your case...

without seeing the contents, it's hard to tell, but what you can do is to put a glass/plastic panell on the side of the case and then use a smoke source, some incense or something and actually see how the air is flowing.

This way you shold be able to easily identify the components that are blocking the air flow and all the hotspots, and then mod your case accordingly...

--------------------
Procrastinate Now!

 

[ceh4702]

You might be able to put heat spreaders on the memory or possibly shift some of the cards around. I dont imagine you want to install a water cooling kit. If you had vent holes on top maybe some heat would just rise out of the case. If you had an empty CD Drive slot you could use a 5.5 bay air intake device.

If you do not like my post feel free to point out your opinion or my errors.

 

[Frank4d]

Here's a picture of the computer I took this morning.

http://users.adelphia.net/~frankford/computer.gif

The problem area is the two boards at the bottom. The bottom one has two G4 processors with finned heatsinks and fans. The board above it has a finned heatsink with no fan, and is behind the other one. 72 watts for w boards.

There is a 150mm fan to the left blowing air on the cards, but the dual Xeon processor heatsinks and fans on the CPU card get most of that air. Probably nothing going between the two hot boards.

I think I'll try the plastic cover and smoke trick to see how much air is moving and where.

 

[Frank4d]

Well I did the 1/4 inch x 6 inch strip of paper hanging in the space between the cards test. The paper almost didn't move. I think I'll buy a couple of fans with filters and cut a couple of holes in the case cover directly above the problem area.

 

[Budley]

Wow! That's a card beast. My best guess would be 2 smaller fans over the cards and the another on the opposite side toward the PSU a bit but still in the same enclosure as the cards. The two smaller fans would be blowing air down onto the cards and the other fan would need to be configured to pull air out. Ofcourse, this is a noisy solution, but you did say that wasn't a concern. Unless there is a heat problem in the area where the PSU is sitting, I wouldn't mod that area.

 

[franklin97355]

Remove the cables stuffed between the cards and move the two slot covers there too. you can get fans that fit in a card slot to add more airflow there.