Installation is simple for most video cards, but when you package two cores onto one PCB, you create a long card. That's exactly the problem with the Sapphire HD 4850 X2. The 11.25" span will make it a very tight squeeze in most cases. It's unfortunate that AMD has not updated their to ensure it fits inside your existing chassis.
When installed in my Antec 900, the card butted into the hard drive bay. Lucky for me there wasn't anything in the way. I installed the drivers that were available on the included CD - Catalyst 8.11 (8.542 RC1).
To overclock the video card, you're very limited with the Catalyst Control Center. The maximum setting is 700/1200 which isn't a lot. To maximize your potential, download the latest version of and . Overclocking is a manual process with AMD GPU Clock Tool as ATI Tool doesn't support the newer cards. However, get a copy as you'll want to do a stress test and make sure your new settings are stable. Slowly increase the core speed until ATI Tool's stress test starts giving you artifacts. I work in increments of 25 MHz and then 5 to fine tune. Once you have a stable core setting, do the same for the memory until you've achieved your maximum overclock. At the end of the day, I hit the wall at 720/2220. This is up from 685/1986. It's a modest gain of 5% on the core and 11.8% on the memory.
To find the maximum temperature, I opted to use . A popular OpenGL benchmark, if you don't get artifacts after 1 hour of running this badboy, your overclocked card is definitely stable. Going to the extreme, I let FurMark run for four hours and after that my temperatures were the following:
Many early reviews stated that this card is extremely loud. However, a recently received BIOS flash fixes that problem. At idle the card is just as loud as my HD 4850 IceQ, which isn't very. From the temperatures above, you shouldn't need to worry about overheating with the new BIOS even at full loud as the fan will pick up then. Just to note, all of my tests were done with the new BIOS. The old BIOS was geared towards performance but won't be representative of what's likely available in stores.