I just bought an XFX Radeon 4870 card, and it's running beautifully, but it tends to get EXTREMELY hot under load - up to 90 degrees Celsius. The design of my case is such that the fan on top of the card dumps all the hot air right up into the PSU fan, which is on the bottom of the PSU, and then it all gets shot out the power supply's vents on the back. Is this something I should be concerned about? It seems to be that a PSU would be able to tolerate fairly high temperatures, but I want to make sure.
I've got a Corsair 620HX power supply, by the way, which has a 120 mm fan on the bottom.
it will be fine, but what you really have to worry about is the gfx card, you need to cool it down a little, re adjust the fan setup so that hot air is drawn away from the gfx card and cold air is blown on to the back of the gfx card
The Radeon 48XX series gets VERY hot, my 4850 was nearing 110 degrees Centigrade with stock cooling! I installed a Thermaltake DuOrb VGA cooler for around $30 and lowered temps in HALF! The 4870 has a better cooler stock but honestly, 90 degrees is normal and acceptable for your GPU... Although definitely feel free to put an aftermarket cooler on it.
So 90 seems a bit higher than the 82 we should expect.....but not too outta line.
many manufacturers are moving to put PSU's at bottom for precisely that reason......but PSU manufacturer's have been dealing with it for years and the good ones won't blink. Of course they will be quite a bit nosier as fan ramps up.