jtenorj :
I wish I had thought to mention this earlier, and the topic will likely be closed by mousemonkey shortly, but the
fan speed profile of a card can be adjusted to a combo of noise the user can tolerate and best cooling performance.
If the HIS was a little quieter but not as good at cooling, a change in fan speed would likely serve to even things up.
It wasn't a huge difference(compared to say gtx480 and temps of 95c). Temps in the 60s and even 70s are fine
for a graphics card. A moderate oc on the HIS might not require any adjustment of fan profiles, leaving it quiet while
still keeping the gpu relatively cool.
Since catalyst (11 ish), the fan profile is uniformly adjusted by driver and not by BIOS or vendor programming anymore. You can count on the fact that a review of AMD cards at current drivers will have default fan profiles set identically. UNLESS the reviewer set the fan speed in catalyst over drive to a manual %. ALSO, not all custom cooling solutions support AMD's driver commands to change fan speeds to set custom speeds. The HIS 7750, for example has only a 2 PIN fan connector, which means it is extremely unlikely to support fan speed adjustments. The ASUS is a full 4 pin PWM with a dedicated sensing logic that can be controlled by the AMD drivers, and thus fully supports AMD's fan speed control commands. ASUS used to use these 2 pin, non-controllable heatsinks (nearly identical to the HIS) back in the HD4000 series, I have 2 of those, and they are NOT capable of fan speed adjustment because there is no onboard logic chip that controls/senses the fan speed (no additional fan speed wire, and no PWM control wire. You need at least the former for this to work). Since the HD5000 series, ASUS added 3/4 pin fan controls, and since HD6000 series, the shroud has been added.
Also the shrouds on these video cards do serve a crucial function. It prevents recirculation of warm air. Without the shroud, on the older type of heatsink designs like the HIS (which ASUS also used in the HD5000 and HD4000 series), the exhausted air circulates a short distance and is re-sucked into the fan in take side. The shroud enlarges this circulation distance and encourages mixing of exhaust air with the case flow. This works on the same principal (but opposite in application) as how adding a layer of transparent plastic to your windows in the winter can reduce heat losses. The plastic itself is very thin, so there is no thermal insulation, but due to the entrapment of air between the plastic and the window panes, the convection cell size has been reduced, so now thermal convections requires 2 cells to reach the window panes. On the shrouded video cards (if done properly), the idea is to enlarge the air flow path between the intake side and exhaust side to encourage mixing with case air flow, to lower temperatures. The non-shrouded cards do particularly poorly in enclosed environments like Shuttle XPCs, etc.
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