First post here - love this community already and lots of helpful posts on modding for less noise. Have to run a small lab for VMware certs out of my home office and replacing a stack of 3750s with a 7250-48p and 8x licensed 10Gb ports. Already that is quieter, but not enough for me to be happy yet. I've read all of the fan mod threads multiple times and essentially it seems that there's a comedy of issues with the fan mods leading to people using wood screws to wedge fans on top of the ASIC heatsink to cool it down after putting in slower fans - otherwise the system might ramp up to speed 2 indefinitely or might switch between speed 1 and speed 2 relentlessly since slower fans move less air and cause the ASIC to go to speed 2. Top this with the fact that it sounds like the board itself requires a minimum RPM to boot and you can either put in fans that meet this RPM or you can spoof the signal - which is also quite tedious.
Annoyed slightly by this issue, I started thinking about re-applying thermal paste - because I didn't quite understand how my switch could idle at 58C on the ASIC with 68-70F ambient temps when I literally only had a serial cable plugged into it and nothing else. I think the thing deterring people from doing this is that it's very difficult to do without damaging the switch. The heat sink is mounted with push pins that typically require you to have access to the other side of the board to get them out. Once the pins are in, they're not coming out without some serious persuasion.
So I tried to take the circuit board out only to find that it's literally riveted to the switch chassis and practically impossible. What followed was almost 60 minutes of me trying to get these things out without damaging the circuit board. I think I may have been successful overall. I had to remove everything down to the board to work in the space. Small warning- the fins arekind of edgy - I sliced my finger tips twice getting this out proceeded by dousing them in alcohol when I was cleaning the junk off the heatsink/asic.
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And what I found is in my opinion utter stupidity. If you've applied thermal compound to a heat sink before, you know that the best practice is a very thin layer of compound to aid the transmission of heat. Too thick and you lose effectiveness. CPUs call for a compound the size of a grain of rice. What I found left me dumbfounded that this is how this equipment was designed. Perhaps I'm missing some of the finer details of enterprise switching...?
Pre-cleaning
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Post Cleaning
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Board after the fact - you can see a little scratching around the holes, but that should be fine given they're no circuitry there.
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So I'm in a spot where I'd like to put a better heatsink on here - preferably one with a small fan integrated. The problem is that the heatsink literally doesn't have a part number and I cannot find any reference for the size / compatibility. I measure it to be approx 65mmx70mm 10mm fins and 2 push-pin mounts. There's nothing out there that fits the bill ... everything on digi and a few other sites are mostly square.
So I might just have to reapply paste and mount the heatsink. I think I have to replace the push-pins as I kind of mangled them getting them out - not really an issue as they're cheap I believe 3MM, and I can put slightly stronger springs on them this time around if I have to go that direction to improve contact with the ASIC.
Anyone know where I can get specs on this heatsink? I imagine re-applying good paste to the heatsink (like MX4 thermal compound or ceramique) could go a long ways here to improving temperatures given the previous situations.
I wanted to follow this posted up with an update. Yes, I need to clean out some dust.
I've been successfully running a modded 7250-48P for the last 9 months 24/7 in my closet and I'm finally getting pics for folks because I had to take down the lab due to a move. I didn't get exactly the temperature results that I wanted, however I did achieve the overall goal of being able to run this switch 5 feet away from my desk behind some accordion-style closet doors with very little disturbance. In hindsight, removing the heat sink probably wasn't the best idea, but I learned quite a bit along the way about heat dissipation and even ended up crimping my own molex power cables.
- Successfully maintained speed 1 at all times. I tested to see how hot I could let it get, so I opened my window on a hot day and it hit speed 2 one time when I hit ambient temps of between 78-80 degrees.
- ASIC Temps generally ranged between 62 and 68 - this is due the limitations I ran into with the heatsink size
- Ultra-Quiet Operations - I don't have a measurement for this, but my R620 running at 10% was louder
I found a company called Advanced Thermal Solutions (ATS) that builds heatsinks, heatsink attachments, and other cooling components. Their product
MaxiGRIP and
SuperGRIP can attach a heatsink or heatsink & fan to literally any ASIC without requiring pins or screws. It's pretty slick and has many different applications - so all you modders out there - check it out. The reason I had to lean in this direction is because I couldn't find anything on Digi-Key that would work with the pre-dilled holes in the mainboard for the stock heatsink (it's a very unique shape). So I had to find a solution that would fit within the standard 5mm clearance around the 35x35mm ASIC. It took a little bit of trial and error, but I was eventually able to find a combination that worked.
- 3x
Mechatronics Fan 40x40x20 fans
- 1x
ATS FanSINK 35x35x14.5mm
- 1x
30x30x10mm12vDC Fan
- 1x
Crimping Tool
- 1x
10-pack Molex Female House 2510 Pins
The heat sink comes with some pretty decent phase change material on it. Wwhen you re-wire all the fans, you must remember that Brocade has a unique wiring methodology.
Black = Ground
Yellow = 12V
Green = Sensor
So when you re-wire these fans, be careful to match the wires with the right pins!
You can wire the ASIC fan into any one of the chassis fans and it works perfectly fine (only the chassis sensor reports to the mainboard as there is no sensor wire on the ASIC fan). As others have said, the sensor freaks out if your chassis fans are spinning less than a certain RPM (I forget exactly what threshold is, but somewhere in the 7-9K mark) and makes everything run in speed 2. So you need to have fans running fast enough to not trigger that. After much research, I settled on the chassis fans above. Also, I turned the fans to blow IN towards the ASIC (back to front) and this got me down another degree or two.
The FanSINK kit comes with a MaxiGRIP attachment. MaxiGRIP technically needs 7mm clearance on all sides of the ASIC and the actual engineered standard is 5mm, which Brocade follows on the 7250. SuperGRIP only needs 5mm, but SuperGRIP cannot handle FanSINK, so I bought and tested the MaxiGRIP and it's miraculously workable and just barely misses a couple of items on the mainboard you'll see in pictures.
Again, ATS MaxiGRIP and SuperGRIP ASIC attachments can work on almost ANY ASIC and come in varying sizes. Super handy.
Here's some pics of what it looked like. And to finish, I'm not sure I'd recommend this approach to anyone because taking that stock heatsink off was pretty dangerous and I could have slipped and screwed something up. I'm sure there was a right was to do it (like removing the mainboard first), but really, just find a good 40x40mm or 50x50mm fan and figure out how to toss it on top of that stock heatsink and wire it into the power for one of the fans like I did here is probably a lot easier and potentially more effective. But keep this fix in mind for your next project.
