Here’s a quick reminder of our $4000 PC component list and prices.

Inspired by our previous 4.35GHz overclock using the same Intel Core 2 Duo QX9650 processor, we wondered how much farther the newer nForce 790i SLI of Asus’ Striker II Extreme could take us. Our March marathon had after all relied on the 780i SLI equipped Striker II Formula, and everyone knows that the 780i is nothing more than an aging 680i with a PCI Express 2.0 hub attached. Surely the knew chipset would have a positive effect.

Changes to this month’s $4,000 build were the motherboard, memory, audio card, graphics, and hard drive. Of these only the motherboard could limit CPU overclocking, because the memory speed can be decreased far below its frequency limit and the other components are supposed to be on fixed-frequency busses. We used the same 1.45V core voltage limit to aid in system longevity, along with the same 1.50V front side bus and Northbridge voltages. We also slowed the memory well below its rated speed for initial CPU stability tests, raising it only after finding the CPU limit. These precautions yielded the following maximum speed.

That’s right, our processor’s maximum stable limit was a whopping 193 MHz lower when using the 790i-equipped Striker II Extreme than it had been when using the 780i-equpped Striker II formula. Could this spell trouble for nVidia’s latest chipset? Our upcoming 790i Motherboard Comparison should provide some answers.

A lower overclock simply adds to the disappointment we already felt about the new configuration after our 9800 GX2 SLI pair proved less capable on average than an ancient pair of 8800 GTX’, but at least the new motherboard offers the bandwidth advantage of DDR3.

NVidia’s recent chipsets offer a limited number of “linked” memory ratios and numerous “unlinked” speeds, allowing virtually any stable front side bus frequency to work with nearly any memory. We’ve seen memory performance drop dramatically using some “unlinked” speeds, so we selected an FSB and CPU multiplier to provide the highest stable memory speed at our 4.16 GHz CPU limit.

Patriot Memory’s Extreme Performance PDC34G1333LLK PC3-10666 4 GB dual-channel kit was picked for its low price rather than overclocking performance, yet it was still stable at DDR3-1400 using its DDR3-1333 rated 7-7-7-20 timings.

Finally, it was time to overclock our graphics cards. Though our March $4000 PC was sorely lacking in GPU overclocking capability, the new cards were much more compliant.

A few hours of adjustments and stability tests brought us to the resulting 720 MHz GPU, 1750 MHz shader, and 1080 MHz RAM clock. We might have gotten slightly more from these cards had we the time to test them in smaller 1-2 MHz increments, but we feel comfortable that this was sufficiently near the actual limit to provide scores representative of a longer effort.