The beauty of both the recently announced nForce 4 and Intel i955X offerings of PCI Express based chipsets for the Intel platform are official support of DDR2-667, and in the case of the nForce 4 SLI Intel Edition chipset, complete autonomy between FSB speed and Memory speed.  You can dial in virtually any speed you want for memory or FSB separate of each other, so there should be a lot of flexibility available in BIOS tweaking options.  Let's have a look.

The BIOS: Asus P5ND2-SLI Deluxe Phoenix Award is back

Although Asus gave us an AMI BIOS implementation on our last outing with their P5AD2-E Premium board, this time around it's back to good ol' Phoenix Award.  With respect to overclocking tools, users can select from a number of Front Side Bus and Memory speed setting options, including Asus' AI NOS and AI Overclock modes.  AI NOS (Artificial Intelligent Non Delay Overclocking System) allows users to set a percentage overclock threshold that is triggered at specific load points depending on system usage and available resources.  If the CPU is heavily loaded, NOS will kick in and overclock dynamically and according to percentage settings you plug into the BIOS.  AI Overclock basically is a menu of preset overclocking combinations of CPU and Memory speed. 

And then of course, there's "Expert" mode, our personal favorite, which allows users to dial FSB and Memory speeds completely independent of each other with this board, and then support those speeds if need be with a various voltage tweaks in CPU, Memory, FSB Termination, and even North and Southbridge chipsets.  Finally, there's also a setting called LDT Frequency, which is a clock ratio setting that AMD users are probably familiar with from those recent nForce incarnations.  The nForce 4 SLI Intel Edition chipset actually uses a HyperTransport link to the Southbridge.  As a result users are also given the ability to adjust multipliers off the front side bus with the LDT Frequency option, should overclocked FSB speeds cause that HT link to go unstable.  All told this BIOS is an enthusiast and tweakers dream and as you'll see in the tests that follow, we overclocked our CPUs like crazy with all these tools at our disposal.

Overclocking With The Asus P5ND2-SLI Deluxe OC'ing The 3.73GHz P4 Extreme Edition and a 3.2GHz Pentium 840 Extreme Edition

We decided to try our hand at overclocking both a Pentium 4 Extreme Edition 3.73GHz chip, as well as a Pentium 840 3.2GHz Dual Core CPU with the Asus P5ND2-SLI Deluxe.  Below are a few shots of CPU-Z's report of these chips and our system setup which included some blazing fast new memory from Corsair.

Pentium 4 EE 3.73GHz Stable @ 4.2GHz

Pentium 840 3.2GHz Stable @ 3.52GHz

What we ended up with was an amazing 4.2GHz completely stable overclock on the 3.73GHz stock Pentium 4 EE chip.  This was achieved with the core voltage set to "auto", believe it or not, and the FSB dialed in at 1200MHz (300MHz Quad Data Rate)with 667MHz dialed in on for a DDR2 Memory speed.  In addition, we were also only working with a stock Intel CPU HSF but the test was performed on an open air bench.  However, as you can see above, the P5ND2-SLI and our P4 EE chip were perfectly stable for a long period of time, running both Folding and Prime 95 simultaneously at a relatively modest 62oC.

The Pentium 840 chip was a different animal altogether but things were definitely more CPU limited in this test.  When we dropped the multiplier on the chip to anything below 15X (ie. 14X1066 FSB for 3.73GHz) the chip would boot into WinXP but with only one active core and no HyperThreading capability. We were able to take the FSB up to 900MHz (or a 225MHz Quad Data Rate clock) but the chip would eventually overheat under load with a full system reset.  What we ended at ultimately was a mild 3.52GHz overclock when fully loaded on our bench at 70oC.  Without question the Asus P5ND2-SLI Deluxe is a fantastic board for overclocking the new 6XX series of P4s and the 3.73GHz Extreme Edition with future compatibility to support Dual Core Pentium CPUs as well.  In addition, the ability to adjust Memory speeds completely asynchronous from FSB speeds with this board, most definitely leaves the end user lots of wiggle room for tweaking.