As the topic title says this is a warning to all 5850 overclockers and potentially all 58xx overclockers!
Short version: CHECK YOUR VRM TEMPS!
Long version: Today while setting up my old server as a mining rig with a reference ASUS 5850 i bought recently i was playing around with overclocking and i got up on 1000 core, 900 memory (I'm on a headless linux so i can't downclock memory more than the stupid limit), my Vcore is on 1,21 and set with RadeonVolt
Here's the issue: I don't know if radeonVolt's reading are accurate but with 100% fan and the core @ 71 degrees my VRMs were COOKING! i kid you not they were between 135 and 140 degrees!!!
This in itself isn't a huge problem as VRMs are build to deal with those temperatures however as far as i can see the VRM's on reference 5850 cards are uP6208 (datasheet: http://ceemic.pri.ee/hardware/datasheets/uP6208.pdf
Take a look at page 19 and you'll see this: Operating Junction Temperature Range (Note 4): -40°C to +125°C
and Junction Temperature: 150°C
So as you can see my card is above the supported operating temperature but still below the absolute max temperature of the VRM and my point is that when you do hefty OC's like this you most likely WILL shorten the boards life span, even with 100% fan and good core temperatures