ATI Radeon Xpress 200: Performance, PCI Express & DX9 for Athlon 64

Overclocking: ATI Bullhead

ATI has some stiff competition from nVidia in the Athlon 64 Enthusiast market. nVidia is well known and trusted by AMD enthusiasts who know the nForce3 Ultra and nForce4 will provide the kind of extra performance they are looking for.

Move over, nVidia, because the ATI Reference board reached an amazing 283x10 at 4X HyperTransport and 2.5-3-3-10 memory timings.

Front Side Bus Overclocking Testbed
Default Voltage
Processor:	Athlon 64 FX55 2.6GHz
CPU Voltage:	1.5V (default)
Cooling:	Thermaltake Silent Boost K8 Heatsink/Fan
Power Supply:	OCZ Power Stream 520W
Memory:	OCZ PC3200 EL Platinum Rev. 2
Hard Drive:	Seagate 120MB PATA (IDE) 8MB Cache
Maximum OC: (Standard Ratio)	224x13, 2912MHz (+12%), 1:1 DC Mode, 2-2-2-10 memory timings, 5X HT, 2.6V
Maximum FSB: (Lower Ratio)	283 x 10 (2813MHz), 2 dimms, 1:1 DC mode, 2.5-3-3-10 1T memory timings, 4X HT, 2.85V

Using Hynix Rev. B double-sided memory, we were also able to reach a 291 (DDR582) overclock, matching the highest overclock that we have ever achieved in testing with DS DIMMs in Dual-Channel mode. The timings and bandwidth were lower at 291, which also required 2X HT, since 3X was not an option in the ATI RX480 BIOS. ATI tells us that 3X will be implemented in production BIOS for the Bullhead board. 283x10 at 2.5-3-3-10 gave the highest memory bandwidth available on the ATI with our standard overclocking test setup.

Intrigued by the performance of double-sided DIMMs in dual-channel mode, we asked ATI about the highest performance dual-channel overclocking that they had achieved with the RX480 in their labs. ATI shared results and timings using 2 single-sided 256MB PQI DIMMs at 2.5-4-4-9 1T timings, at a frequency of 313 or DDR616. We did not have single-sided Hynix B DIMMs in the lab to try to duplicate ATI's test setup. However, based on our results with DS DIMMs, we have no reason to doubt their results. If you compare these overclocks to the outstanding overclocking capabilities that we found with the DFI LANParty UT nF3-250Gb, you will see that the ATI Bullhead is reaching further in Dual-Channel mode than the highest clock speed that we could reach in single-channel mode on the Socket 754 DFI.

In our opinion, ATI has more than succeeded in their goal of proving to computer enthusiasts that the RX480 is a chipset for serious performance overclocking. These are, overall, the best overclocking results that we have ever seen with an Athlon 64 motherboard. The fact that these were achieved on a Reference board is all the more amazing!

Front Side Bus Stress Test Results:

As part of our overclocking tests, a full range of stress tests and benchmarks were run to make certain that the ATI RX480 Bullhead was stable at each overclocked FSB speed. This included Prime95 torture tests and the addition of other tasks while Prime95 was running in the background. Many motherboards reach high overclocks and then behave as if they are on the ragged edge at those high overclocks. The ATI Bullhead was remarkably stable at both 224x13 (CPU Limited) and the even more challenging 283x10. For maximum stability at both settings, we needed a modest increase in CPU voltage to 1.55V, but at that setting, we were able to loop benchmarks for several hours without a system failure.