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When ATI released their X1900 series of Radeon PCI-e graphics cards, voltage requirements quickly became apparent. CrossFire cards need a lot of clean juice to run stably. Whether or not you want to fault ATI, the fact remains that an X1900XT or X1900XTX CrossFire system requires a certain quality of PSU to run reliably. ATI actually keeps a list of CrossFire "Certified" PSUs for each of their generation of high end cards, and a few months ago the X1900 list only had around 3 PSUs, two from FSP and one from Antec. We reviewed FSP's excellent Epsilon 700W PSU already recently, but since then the list has grown to a respectable 12 PSUs, including 2 of Antec's 550W models. The GameXStream is yet to be added to ATI's list, but we're told it is under certification testing right now at ATI. Perhaps we can help out and explore ourselves just how stable the GameXStream is with CrossFire.

Here's the system we put together.

• ASUS A8R32-MVP Deluxe Motherboard
• DualATI Radeon X1900 16x PCI-e Graphics cards in CrossFire
• CPU?
• 2 x 512 megOCZ PC4200 EL Platinum Edition memory
• Western Digital WD1200 Caviar SATA Hard Drive
• Samsung SH-W162 DVD +- R/RW Drive
• Microsoft Windows XP Professional SP2

And tack onto of that our OCZ GameXStream 700W Power Supply. That is a solid system if I ever saw one.

As I mentioned, we have had experiences here with power supplies of otherwise excellent caliber (in the 550 and 600W range) that couldn't handle CrossFire. Here's a small list of those for which have been given stamp of approval upon ATI's list of CrossFire "Certified" PSUs.

• Thermaltake ToughPower 550W (W0096RE)
• Sin Tek 600W
• Antec TruePower 2.0, 550W
• Sparkle FSP550-60PPLG (550W)
• Antec Neo HE550 550watt
• Sparkle FSP650-80GLC (650W)
• Thermaltake Purepower 680W (W0049)
• FSP EPSILON FX700-GLN

To satisfy our own curiosity, we ran what could be considered one of the most taxing applications for both GPU and CPU performance, 3DMark 2006. Most other non-certified PSUs we've tested failed on this setup. It does put enough load on CrossFire to destabilize "regular" PSUs. Here's the figures the three voltage rails read during our testing.

We ran 3D Mark with the Shader Model 2.0 and Shader Model 3.0 with HDR(High Dynamic Range imaging), the most intense test we've noticed in the past. Every single run perfectly, without so much as a hitch. By comparison, other PSUs tend to crash, lock, or reboot the system after a certain period of time running the test. On a couple of added notes, we even ran a session of 3DMark 2006 while 2 instances of CPU Burn-in ran in the background. That leads to the second point. Someone propped up a thermometer right behind the exhaust vent for the two cards. The Mercury topped out at 50 Celsius. Pretty hot.