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.
Because it's designed to operate at those temperatures. 24x7x365. For years. These are not consumer junk. The max die on these processors is 105C+, all of the capacitors are 85C rated or above, and it is designed to run at these temperatures and higher without failing. They get thrown into the top of a rack with terrible airflow design at
best, with 30U+ of heat source directly below, and next to no cold air supply. And that's the least severe duty they do.
And believe me, I would know. I've been engineering the systems that rack below these for decades. Brocade's one of the few I'm not aware of having successfully cooked out when located in the same rack as one of my heat exchanger equipped systems. Even when basically starved of cold air supply and sitting in a rack with more than 8kW draw, it was fine.
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.
That's not thermal paste. That's a perfectly good reusable thermal pad, which you ruined. They get used in this sort of application because they do not wear out or dry out. (No, that was not dried out. It was perfectly fine till you separated it from the woven layer.) And they're more tolerant of severely unlevel IHS and CPU mounting. That IHS gets slapped on there with some glue to protect the die and give them somewhere for a pretty part label, not be a critical heat transfer element.
And no, you can't just buy replacement. The particular compound they used there is familiar to me, and only sold in bulk roll. And no, you can't just slap some AS5 or GC12 on and 'fix' it; the woven compound is impregnated.
Thermal compound is not going to improve performance meaningfully at all. These are very, very low TDP parts. All the heat load is in the POE board. You could strap an Alpha cast copper slug on there and it wouldn't net you anything significant. Which is why they're just fine with a cheap, loose coupled, cast aluminum part that isn't even in direct airflow but go to pains to route over the POE board. So basically anything that matches the pin span (which is measured center to center with a caliper) and fits within the keepout zone indicated by the outer white box will work fine.
No, really. Whatever. Doesn't matter. It'll be fine. Effectively coupling will be a whole other story, but, it won't break anything.