Video Cards, Motherboard, And Case
Video Cards: 4 x Gigabyte GV-R485OC-1GH in CrossFire
This was the choice that shaped the build, which is obviously the most controversial component in the list. Why did I choose four Radeon HD 4850s? Let me guide you through the thought process.
I wanted to make this AMD box a formidable gaming machine, and to do that, I needed to consider some real horsepower. In fact, I originally tried to fit two Radeon HD 4870 X2 cards into the budget. I could have made it work, but the tradeoffs would have been hard to live with: we would have had to settle for a dual-core Phenom II X2 550 or a triple-core Phenom II X2 710 to make it workable. In addition, we would have had to spec out a monster power supply capable of handling a pair of mammoth Radeon HD 4870 X2 cards.
The next logical step was to use four 512MB Radeon HD 4870s instead, to save money. This allowed us to budget a true quad-core Phenom II, a better motherboard, and a nicer case. Unfortunately, we couldn't find a suitable PSU at a reasonable price that we were confident could handle our quartet of Radeon HD 4870s. Remember that each card would require two PCI Express (PCIe) power cables just to run the graphics subsystem alone. Yes, we could have used molex-to-PCIe adapters, but we weren't confident it would be a good choice for a stable system, because we didn't have all the money in the world to spend on a top-tier power supply.
Then it occurred to us: why not use Radeon HD 4850s? This choice would allow us to get cards with 1GB of memory instead of 512MB, and we could get overclocked models that would perform closer to the Radeon HD 4870s we craved while remaining within our budget. Lo and behold, we found Gigabyte's GV-R485OC-1GH, and it fit the bill so nicely:
With a 700 MHz core clock rate (versus the reference 625 MHz) and a full gigabyte of memory (not to mention a nice, quiet aftermarket cooler) each GV-R485OC-1GH gave us just what we needed at a low $120 price tag.
Will four of them provide epic gaming leetness? For the price, maybe. We're well aware that CrossFire provides diminishing returns as we scale up, especially past two cards. It might turn out that we could have been better served by two Radeon HD 4890s. It might turn out that the low-end pair of Radeon HD 4850s in CrossFire matches the system's performance due to driver limitations. But you know what? We're doing it anyway, just because we want to see what it can do.
Motherboard: MSI 790FX-GD70
We weren't kidding when we said the decision to go with four graphics cards heavily affected every choice thereafter. For example, it was the MSI 790FX-GD70 or nothing, as we couldn't find any other motherboard that would provide the usable space for four dual-slot Radeons in CrossFire.
Sure, there were other boards with four PCIe slots out there, but most of them will only realistically handle three dual-slot graphics cards because of the way the slots are spaced. But just because we didn't have a choice doesn't mean we were disappointed. The 790FX chipset is ideal for our purposes, and MSI's board has an excellent reputation as an enthusiast piece. At $165, it ate up a good chunk of our budget, but it was worth every penny.
Chassis: NZXT Tempest Mid-Tower Case
Now that we have a motherboard and graphics card, where are we going to put them? Our experience has shown us that the NZXT Tempest is a great case with a lot of airflow. But more importantly for this specific application, it offers a lot of space for graphics cards. Even with the power supply mounted below the ATX-sized motherboard, the Tempest leaves us more room than a lot of its competitors, which makes it an easy pick. The $100 price tag is reasonable, too.