BIOS and Overclocking
Now we get down to what nVidia has done for the overclockers. From the beginning, we were told that this chipset would be for overclockers and that the reference design would reflect that in not only layout but BIOS as well.
The BIOS used is a standard Award 6.0 modular BIOS, in fact it looks like any other BIOS out there. We thought that we were given a bum steer with this board as there are no extra menus like other companies put into their BIOS for Overclocking options.
To get to the Overclocking menus you simply look under Advanced Chipset Features menu, here you get the Overclocking setup. There are four major menus with Overclocking, System Clocks, FSB and Mem config, CPU configurations and System Voltages.
Starting with System Clocks is where you find the setup for the three PCI Express x16 frequency clocks. All three slots can be controlled independently of each other. Each slot can be run from 100MHz to a max of 200MHz in 1MHz increments. PCI Express clocks should not be touched as they tend to cause instability in the system - only play with these settings if you really know what you're doing.
The SPP MCP Reference clock is the base speed that the HT link between the North and Southbridges run at. This clock is then set with a multiplier like a CPU is to get is full speed. The ref clock speed can be adjusted from 200MHz up to 500MHz in 1MHz increments.
Next comes the multipliers for the HT link for upstream and downstream. These range from 1x to 5x on both. For best results and stability, set the SPP to MCP ref clock to 200MHz and the multipliers to 5x to allow best possible overclocks.
Lastly in this menu is the Spread Spectrum clocks, nVidia recommend disabling all of these for overclocking as it will only hinder the voltage regulators supplying the right amount of currant to the components.
Moving to the FSB and Mem Config menu, we find this is where you change FSB and memory settings as well as the CPU multiplier. The FSB - Mem clock mode has three settings - Auto, Linked and Unlinked. When in Auto you can't change any settings in BIOS. When in linked mode, the FSB and memory are linked together using ratio dividers, the higher the FSB goes the higher the memory goes. Unlinked mode allows you to change the FSB independent of the memory and vice versa - this way you can get the most out of the FSB and then overclock the memory to match rather than having one part hold you back - we love this feature!
When unlinked mode is set the FSB and memory setting are unlocked. nVidia and eVGA have put the FSB speed in QDR rather than the reference clock rate. This means you can go from 400MHz (100MHz) to a max of 2500MHz (625MHz) in 1MHz increments.
Memory is set in DDR rate, so you can go from 400MHz (200MHz) to a max of 1400MHz (700MHz) in 1MHz increments.
The CPU Configuration menu has a couple of interesting options. You can enable or disable the CPU thermal management as well as select what Thermal Management the CPU uses - either TM1 or TM2 if your CPU supports that.
Also if you have two or more cores on the CPU, you can disable any one of them with this option but you will only want that for testing purposes - it is much better to leave them all running for a faster system.
Lastly we have the System voltages, and thy people at nVidia and eVGA have done a good job here. Here you have CPU Core, CPU FSB, Memory, SPP, MCP and SPP to MCP voltages.
CPU Voltage ranges from as low at 0.9375 all the way to 1.8v in 0.025v increments.
CPU FSB voltage ranges from 1.2v to 1.5v in 0.1v increments.
Memory ranges from 1.8v to 2.5v in 0.025v increments
SPP voltage ranges from 1.2v to 1.55v in 0.05v increments
MCP voltage ranges from 1.5v to 1.75v in 0.05v increments
Lastly the SPP to MCP HT link voltage ranges from 1.2v to 1.55v in 0.05v increments
With all this we managed a huge and stable FSB of 488MHz (1952MHz QDR). To do this we had our Core 2 Extreme at 6x multiplier resulting in 2928MHz, FSB at 1952MHz QDR, memory at 1005MHz DDR, HT Ref at 200MHz, HT multipliers at 5x. As far as voltages go - CPU voltage at 1.400v, Memory at 2.2v, FSB voltage at 1.4v, SPP voltage at 1.3v, MCP voltage at 1.65v and HT link at 1.3v.
Suffice to say, we were really impressed with the FSB overclocking result of the nForce 680i chipset and it matches any other Intel Core 2 motherboard we have tested to date. We can't wait to see what other companies can do when they release their own finely-tuned motherboards.