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You are here: MacNN Forums > Hardware - Troubleshooting and Discussion > Mac Desktops > Cooling FB-DIMMs

Cooling FB-DIMMs
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Jul 25, 2013, 06:35 PM
 
So I wanted more RAM for my Xserve but for some reason the 800MHz FB-DIMMS are much rarer and more expensive than the 600MHz versions.

I bought some Mac Pro sticks on eBay since I got 6GB for the price 2 or so. I figure the heat sinks are different because the Mac Pro runs quiet but the Xserve is pushing some serious air through with fans up to 12000rpm.

I bought some cheap off the shelf heat spreaders but they aren't going to fit. Anyone ever seen any for sale to fit FB-DIMMS? They have small chips on them that have thermal paste applied.
I have plenty of more important things to do, if only I could bring myself to do them....
     
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Jul 26, 2013, 05:50 AM
 
So the 6GB I got was a pair of 2GB sticks and four 1Gb sticks.

I already have four 1GB sticks, so I figured I'd end up with two of those spare to resell or whatever.
I have managed to fit a pair of standard DIMM heat spreaders to a pair of 1GB sticks. I'll test those later and see what sort of temps they get to but they standard heat spreaders don't make proper contact with all the RAM chips on the 2GB sticks so I can't get away with that.

I can't find anywhere selling the proper heat spreaders for these FB-DIMMs. The spreaders are fairly common, there is plenty of server RAM using them from Dell, HP etc as well as aftermarket from Hynix and Crucial etc but I can't find the heat spreaders on their own. I' don't suppose anyone has any old dead or small capacity FB-DIMMs going spare anywhere?
I have plenty of more important things to do, if only I could bring myself to do them....
     
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Jul 27, 2013, 01:02 PM
 
So I swapped out the monster Apple-issue Mac Pro RAM heat spreaders for some generic cheap and nasty ones I got online for 40p each. These wouldn't fit the 2GB DIMMs so I put them on all four of the 1GB sticks.

I installed them all and fired up the Xserve to test. Fans made a couple of unusual noises but then it booted normally. All RAM recognised, so far so good.
I loaded up Server Monitor so I could keep an eye on the RAM temps and then kicked off a 25 minute 702p MKZ converting to MP4 with Handbrake and proceeded to watch the temp graphs.

It all started out fine. Two of the new modules were a little on the warm side. a shade below 60C while the other 6 were all just above 40C. They started to climb to 63C or so and then the fans ramped up and the temps started to drop back to more like 57C. Server Monitored never wavered from claiming these temps to be normal so I thought everything was fine.

About five minutes later, the fans started what I can only describe as 'throbbing' where they would ramp up, then down quite quickly. It seemed to be several fans doing this in unison. When this happened, the memory temps vanished from the list in Server Monitor altogether so I decided it was best to shut down at this point.

So I'm back hunting for a source for some proper OEM style heat spreaders. I notice that HP and Dell have used the same type in some of their servers. Does anyone have any dead FB-DIMMs lying around they want to sell?
I have plenty of more important things to do, if only I could bring myself to do them....
     
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Jul 28, 2013, 01:55 AM
 
Have you tried to contact Kingston there in the UK.? When two of my (Mac Pro 1,1) RAM modules died, I had to send them back there in order to get a replacement (life-time warranty) so maybe they have dead modules os just the heatsinks stored somewhere…

customerservice AT kingston-technology DOT com
( Last edited by angelmb; Jul 28, 2013 at 03:48 AM. )
     
   
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