When first testing the Nvidia nForce4 SLI X16 we saw the ASUS A8N32-SLI Deluxe mainboard, based on that chipset, delivering a lower performance across a number of tests than the ASUS A8N-SLI Premium, a mainboard on the ordinary nForce4 SLI, did (for details see our review called Dressed to Kill: ASUS A8N32-SLI Deluxe Mainboard Review ). The difference wasn’t too great and mostly showed up in synthetic tests. As for games, there was a gap of just 1-2% between the two mainboards.
We rechecked the results repeatedly, but with the same outcome, so we couldn’t but come to the conclusion that the new SLI-compatible chipset from Nvidia with two complete PCI Express x16 slots didn’t offer any real advantages over the older, “PCI Express x8 + x8” chipset. But we were wrong.
According to the documentation we had at that moment from Nvidia, the North Bridge of the nForce4 SLI X16 was connected to the CPU via two 8-bit HyperTransport channels. The width of the channels between the North and South Bridges is 16 bits. Our changing the appropriate BIOS setting had no effect on the performance. Since the PCI Express x16 slots are governed by the different Bridges in this chipset, we thought Nvidia had sacrificed the bandwidth of the HyperTransport bus on the CPU – North Bridge line to make the graphical slots complete. This was indirectly confirmed by the results of the tests. Moreover, we set the width of the link between the North and South Bridge to 8 bits by following the incorrect BIOS setup procedure also given in the documentation and this limited the performance further.
As it turned out eventually, there was an error in the documentation and the lower performance of the ASUS A8N32-SLI was caused by quite another factor, which we will discuss in the next section of the review.