Want to see how many watts I can save by switching from an old 40GB HDD to a USB stick.
10W, max. Less if the HDD spins down regularly.
I typically aim for 80C, but willing to go above. I see people in here running their sh!1 @ 90C and I'm like D: I know these cards are built for it, but what's the industry standard, rule of thumb, etc. for temps?
290's can run hotter than 79xx's.
http://anandtech.com/show/7457/the-radeon-r9-290x-review/19
Seems the 7970 tops out around 80C, 290X's go up to 90C+. 6970 and 5870 get warmer than 7970 due to the older 40nm process.
Can't believe anyone would use an enclosed case for a dedicated miner, unless it's water cooled.
An enclosed case actually can provide better cooling than a semi-open one. Completely open, ok, as long as there's good airflow in the room (large fans) then I guess it's best. But cases can provide directed airflow, which is better than random airflow. If you have fans in an open case, the air that they're moving isn't going in a concerted direction. The best case designs pull cool air in from one part of the case, direct it over the hot components, and exhaust it out another part of the case. Usually this is a front-to-back motion, but there are other ways as well (e.g. side intake, top exhaust). As long as the intake and exhaust airflow are balanced, you can get pretty good results.
If you have a good flowing case like I described above, all the hot air is exhausted out the back of the case, and it can't get back inside because the fans in the back, and the walls on the sides, keep it out. For that hot air to re-circulate through the case, it has to make its way all the way around to the front. With an open design, heat from one video card might just be blown to the CPU, or the RAM, or another video card. It doesn't flow in a uniform direction, it's just blown wherever the fans happen to take it, and it can "pool" in areas that don't get airflow from fans. In fact, case fans can hurt more than they help in open cases, because there isn't anything separating the exhausted air from the intake air. The exhausted air ends up about 6" from the intake air, at most. They can just blow the same semi-warm air around and around in circles.
Say you've got a 120mm case fan in the back of your case, pointing out (exhaust). If the case is closed, it can only exhaust one kind of air: air that's inside the case. If the case is open, it can pull in outside air and exhaust it alongside the hot air. It might flow 100CFM, but if 50 of those CFM isn't hot air from your components then you're just wasting half of it.
If I were a serious miner (multiple GPU's in a chassis) then I would only buy video cards with duct designs that exhaust directly to the rear of the chassis (like the AMD reference designs). The open designs spew their hot air in all directions. Some of that will of course spill over to the other cards in the chassis. Yes, the open design cards can generally perform better in a single-card setup because they generally have huge heatsinks (covering the entire card) and multiple fans, while the ducted designs have smaller heatsinks (only directly on top of the GPU and VRAM) and only have a single fan (at the "front" end). Ideally you would have these large heatsinks, plastic ducts/shrouds around them, and fans blowing laterally along them (front to back of the case) rather than down through them.
I could swear that AT did an article about open/closed case heat performance sometime, maybe 5-10 years ago.