Change a Dell 6850 Motherboard

This is how to change out a Dell 6850 motherboard. If you find yourself with a replacement motherboard and no official tech to change it out for you, you can do it yourself, it isn't that difficult, if you know about the blue button.

These are the steps:
1. take the server out of the rack (or leave it in, whatever)
2. take out the memory modules
3. take out any pcix cards you may have
4. take out the plastic card divider
5. remove the crossbar
6. unplug the cdrom
7. unplug the chassis intrusion connector
8. remove the northbridge heatsink
9. remove the cover from the processors
10. remove the processor heatsinks
11. unplug three cables from motherboard
12. remove the two other boards (only applicable if you have a third and fourth processor)
13. pull the blue button, side the motherboard forward, and lift the back out first
14. clean heatsinks
15. apply thernal grease to all four processors and the northbridge chip
16. move processors from old board to new board. be sure to operate the release levers properly.
17. put new motherboard in, front down first, then slide it back while pulling the blue button up.
(make sure the blue button locks back into place to hold the motherboard in the right spot)
18. plug three cables into new motherboard
19. install processor heatsinks
20. install northbridge heatsink
21. install crossbar
22. install cd rom cable
23. install chassis intrusion connector
24. install two other boards. (only applicable if you have a third and fourth processor)
25. install plastic divider
26. install any pcix cards you may need
27. install memory modules
28. put server back in rack and turn it on


Yes, these are not good pictures. Yes, I took them with a crappy cell phone. Yes, I used a few of them more than once. :)

You can skip this step if you want, but it's a little easier to do this procedure on a bench or table.

There are little blue tabs on the left and right, up near the front that you need to push on. then you can pull the server forward about 1/2 inch and it will come up and off the rails. It's heavy!

If you have the same amount of RAM installed in each module, it doesn't matter what order they go back in, so just pull them out and set them aside for now.

remove any pci/pcix cards you may have in the server

There are two little black tabs you have to push to get this thing to release. Sorry for the fuzzy picture.

There are two black tabs on the sidewalls that you need to push towards the rear of the server. then you can lift the crossbar out. Be careful with the scsi cable attached to the bar if you have one.

it's a scsi cable on the right side, just behind where the crossbar used to be.

It's up by processor four (or processor slot four if you don't have a fourth processor) on the left side, front of the motherboard. it has a black and red wire, and it's kind of hard to get loose. It's near one of the onboard scsi connectors. Be careful not to break it!

The instructions with your new motherboard should have a note included about this step. Do not lift up on the heatsink until the thermal grease under it has let go, or you can damage the chip. Take the strap loose, then gently twist the heatsink clockwise and counterclockwise until you feel it release. Then, gently pull straight up.

This one is a little tricky, because you have to press down in two places while lifting up in four places. The trick is to get the clips loose by pushing down, and then lift the entire panel straight up. If it sticks, it's just in a bind because you didn't lift straight up. Level it out by pushing down on the part that is higher and then try again. The two places you press down to release the clips are clearly marked. (look for two circles with push-down symbols)

carefully remove the processor heatsinks. Push the blue tab down and squeeze the metal bars together while gently pulling up. Then, use the same method as you did for the northbridge- twisting until you can feel that it is free. if you don't do this right you may end up pulling a processor out prematurely.

If you do pull out a processor, just gently pull it from the heatsink, lift the latching lever on the processor socket all the way up, and replace the processor (observe the orientation! #1 and #2 are 180 degrees from #3 and #4!) remembering to put the latching lever all the way back down.

There are three cables (two of them are very stiff) that you need to unplug. Be careful!

If you have a third and/or fourth processor, you'll also have one or two extra boards, to the left of the northbridge. These are held in place like DIMMs, just push the latches away from them and pull them out. Remember where they go!

This is the tricky part! There is a blue button right in the middle of the board. If you pull it up, while pushing the entire board forwards, it will slide about 1/2 inch and be freed from the chassis. Then, just lift the back of the board up and out and the front will follow. Be gentle!

Use the cleaning pads to get all the thermal grease off the heatsinks!

Use the syringes full of thermal grease to squirt the stuff on to every processor and the northbridge chip. You're supposed to go in a spiral, but there really isn't enough to pull that off. It says not to get this stuff on your skin, but you need to smear it around. Use gloves! Or get it on your fingers and lick them clean. Just kidding! Wash your hands though!! 

Carefully take the processors out of the old board and put them (correctly oriented) onto the new board. Be sure to lift the levers all the way up and back to pull out or put in the processors, and also to push the lever all the way back over and down once the processor is in place.

If you paid for onboard RAID, there will be a RAID hardware key installed. You need to get that off the old board and onto your new one. It's located near the back of the board, installed into a blue socket.

To install the new board, just put the front side in first, carefully dodge the plastic bits and the cables that are in the way, then place the back end down, and slide the board backward while pulling the blue tab that locks the thing in place. Make sure the board is locked down before you go to step 18!

make sure to get them seated correctly.

Be gentle. The back part of the latch strap goes in first, then squeeze the front parts together while pushing down on the blue tab.

Put the cover back on too!!

Same as taking it out, in reverse.

This should snap right back into place. Make sure the cd rom cable goes through the notched part of the bar.

You need to make sure the cable is as flat as possible against the outside wall so that the memory module ("A") doesn't bump into it.

Don't forget this one!

If you have a third and/or fourth processor, install the first and/or second "other" board, left of the Northbridge chip.

It only will go in one way. Make sure it clips itself down by gently pulling up after you think you've got it in.

Make sure you put in any cards you took out- if you have a PERC you'll also need to connect the internal scsi cable that goes to the backplane.

(this picture shows a PERC 4/DC without the plastic divider installed, make sure you put in the divider first!!)

Gently put in all your memory modules. When you push the blue tabs down, there are metal spikes that come out of the front and back of the module to hold it in place properly.

If you took it out, put it back in, put the top on, and fire it up!

You may need to set some BIOS options to make it like your old board.

NOTE: My PERC 4/DC somehow lost its settings, even though the battery is fine and the red light stayed on the whole time I had it out of the server. I had to go in and tell it to copy the configuration from the disks to the nvram. If you aren't familiar with the PERC setup, you should have Dell walk you through this, because if you select the wrong options you'll destroy your array and forever loose your data. But you do have a backup, right?!

Hope it worked out for you. Maybe next time the tech will show up to do his job!