kovboi said:
first, i'm not sure the passive ventilation really does that much good. i've experimented with and without open pci slots in my own case and not found any real difference in temps. it might be worth trying out a slot blower either focused on your video card's or motherboard's heatsink, or facilitating ventilation out the back of the case.
Well, with air cooling there's two ways to look at it. One is to leave the case door on, seal everything up, and do a 'wind tunnel' type of config. My extreme air cooled case many machines ago followed this concept, and it was actually cooler to have the case door on than the take it off due to the 'wind tunnel' effect.
When you start getting silent many often find that removing the case door will drop temps slightly. This is because hot air builds up inside the case a bit. Unless you have a real bad setup it's not going to perpetually build in a major way, but it might be a few C higher compared to having the case door off. Lots of passive intakes essentially allows the computer to run 'open', so you're not forcing air in with case fans. The internal fans can pull in their own air without help from the case fans, thus less fans, thus quiet
A few PCI slot covers won't do it, but my setup has a lot of passive intakes in addition to the slot covers.
And yes, dust may be a concern with negative pressure, but blowing in 100CFM with intake fans would suck up just as much! With a lot of passive intakes there's actually not so much suction in any one place, more of a slow-flow of air throughout the case, so I find that dust isn't really an issue. My intake fan gets *much* more dusty than the passive intake areas.
As for temps, I was getting 38-40C idle and 49-51C load @ 2750 1.5v, but I have very high ambient temps around 80F+. My place gets a lot of sun and mad greenhouse effect. In a cooler place those temps would be 2-3C lower (for example, on a cool morning when my ambient dropped to 69F it was around 46-47C load).
GPU does 46-47C idle and 65-68C load (not unusual temps for a 6800 series).
--Illah