Kal-EL
03-05-2009, 01:20 PM
Overclocking Intel's Core i7 920
Manufacturer: Intel (http://www.intel.com/)
We've seen how the "Core" performance lies, but what about stretching the value of a new i7 920 purchase that much more? With an RRP of $284 it’s not exactly a Core 2 Quad Q6600 G0 territory bargain, but it's the cheapest of the new Core i7 CPUs by a large margin.
What potential does $284 buy you though? The Q6600s clocked to between 3.0 and 3.6GHz usually, although inevitably there are some people out there with some serious skills having eked out over 4GHz.
But with a new architecture comes a new way to overclock - we'll walk you through how to get a solid overclock out of the Core i7 920 on two of the latest motherboards, describing what BIOS settings we found worked.
http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/asus1-3.jpg (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/asus1-8.jpg) http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/msi1-3.jpg (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/msi1-8.jpg)
Asus P6T Deluxe and the MSI X58 Eclipse - click to enlarge
Hardware Choices
With the launch of a whole new platform we're currently a little limited when it comes to hardware choices because not everything has arrived at the store-fronts yet. That said, there are two boards we have currently in the office that we’ll try just to see how far both go, although we'll be doing a full review as well so you know the ins and outs in the coming weeks.
In addition to the Core i7 920, we've got the Thermalright Ultra 120 eXtreme 1366-RT and Noctua NH12P with LGA1366 mounting brackets - both offer tremendous cooling power for these 130W TDP CPUs that will be overvolted, increasing their power output.
On the motherboard front we'll be using the MSI X58 Eclipse (http://www.bit-tech.net/hardware/2008/08/26/early-look-msi-x58-eclipse/1) and the Asus P6T Deluxe (http://www.bit-tech.net/hardware/2008/08/21/asus-p6t-deluxe-next-generation-x58-motherb/1) - both of which retail for around £280 here in the UK. Finally we've got a 6GB triple channel Corsair Dominator 2 kit that's rated to 1,600MHz with 8-8-8-24-2T timings at just 1.65V. These should also retail for about $300 (approx. £230) making them an expensive investment.
What's more, because the Core i7 has oodles of memory bandwidth anyway, running triple channel 1,600MHz might not offer the greatest benefits given the price. While we'll investigate how memory bandwidth and latency affects performance specifically in a later article, if we're looking for the most awesome enthusiast platform available, 1,600MHz DDR3 is the way to go at 4GHz simply because it ties in nicely with the Core i7 920 – that’s demonstrated over in the BIOS page.
The rest of the components are identical to those used in the Core i7 review (http://www.bit-tech.net/hardware/2008/11/03/intel-core-i7-920-945-965-review/1) so the results we're quoting here are directly comparable.
Here's how we started out with the Core i7 920...
http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/1-920stocks.png (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/1-920stock.png) http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/2-920stocks.png (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/2-920stock.png) http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/3-920stocks.png (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/3-920stock.png)
We disabled Intel Turbo Mode for these pictures, which causes CPU-Z to read 2.93GHz for the i7 920. Click to enlarge
... and how we ended up after just ten or fifteen minutes of overclocking.
http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/1-4s.png (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/1-4.png) http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/2-4s.png (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/2-4.png) http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/3-4s.png (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/3-4.png)
CPU-Z reads the CAS latency information incorrectly - we had set it at Corsair's specifications of 8-8-8-24-2T in the BIOS. Click to enlarge
Asus P6T Deluxe - Installation
Cracking the board out the box we’re presented with a familiar Asus colour and styled PCB. There are a few new things with the P6T Deluxe we’ve alreadly covered in our early look, and we’ll test them in depth at a later date. However, for those unfamiliar with how to do the basics – here’s a guide to correctly installing a Core i7 CPU, and adding heatsinks and memory to both boards.
http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/b1-3.jpg (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/b1-8.jpg) http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/b2-3.jpg (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/b2-8.jpg) http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/b3-3.jpg (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/b3-8.jpg)
Click to enlarge
The LGA1366 socket is quite a bit different from LGA775, however the seating and mounting mechanism is exactly the same - drop it in (it can only go one way) careful not to displace the tiny pins, then pop the cap over and use the arm to secure it in place. Next, apply some thermal paste over in a thin even spread over the central heatspreader to improve the thermal contact between CPU and heatsink.
http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/b4-3.jpg (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/b4-8.jpg) http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/b5-3.jpg (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/b5-8.jpg) http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/b6-3.jpg (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/b6-8.jpg)
Click to enlarge
Screwing down the new Thermalright Ultra-120 eXtreme-1366 RT is a little tough, but the large springs help create a firmer compression. As the CPU socket itself now has a metal backplate to prevent PCB bending, these high pressure springs should not cause the problem of warping PCBs.
The memory must go in the orange slots first – not the black ones. This is a change to the norm as usually the memory goes into the closest set of memory slots first, but in this case and on the MSI below it’s the set further away.
MSI X58 Eclipse - Installation
To try something different, we've used the Noctua NH-U12P to cool the Core i7 920 on the MSI X58 Eclipse. The CPU is installed in the exact same way as the Asus board, and while the Noctua takes a little extra time to fit the bracket its two sprung screws are far easier to secure than the high pressure ones used on the Thermalright.
http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/msi2-3.jpg (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/msi2-8.jpg) http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/msi3-3.jpg (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/msi3-8.jpg) http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/msi4-3.jpg (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/msi4-8.jpg)
Click to enlarge
Unfortunately this is as far as we got on our early revision 1.1 board. We had set it up, got to know the BIOS a little and overclocked it to 4GHz - matching the Asus - then tried to burn it in a bit with some Prime95. And burn it we did - the board lasted about 30 seconds before one of the memory MOSFETs burnt out in a puff of blue smoke.
We're currently working with MSI to understand why this happened and will update this article in due course. Unfortunately, it's not unusual for early boards off the production line from any manufacturer to either arrive DoA or pop after a short while. We hate to say it but a new batch of a brand new board fresh off the production line occasionally hasn’t got all the manufacturing bugs ironed out. At worst case, MSI has a duff batch of Power-PAK MOSFETs.
We know this having occasionally followed MSI during the board’s design that it’s been tested further than we’ve lightly pushed it here and since we weren’t doing anything untoward it we expect this was simply just a duff part.
Asus P6T Deluxe - BIOS Setup
The Core i7 920 has a 4.8GT/s QPI and a slower northbridge/Uncore frequency than the Core i7 965, which gives it plenty of overhead to dive into. The Core i7 920 CPU is multiplier locked (only the Extreme Edition 965s are unlocked), so we'll have to increase the QPI frequency to get more MHz.
AI Overclock Tuner - Manual: Although if you're lucky enough to have XMP ready memory you might want to try that - 1,600MHz sets the QPI link to 200MHz - just what we needed for 4GHz, but we still did it manually anyway.
Intel Turbo Mode - Disable: We disabled it so as it would not interfere with the overclock, however we left on the new Intel low power states. Normally this affects how the CPU overclocks and in extreme cases we expect it will, because the on/off effect to the CPU frequency and voltages as the C-state changes.
Intel has stopped multiplier dropping its CPUs like it does with Penryn, instead it just turns the clocks and cache off in stages to reduce power of the cores. However considering the CPU has a 130W TDP before overvolting and overclocking, we didn't quite fancy running it all guns blazing all the time (we still need the CPU for future testing!). We found the on-board power microcontroller built into the Nehalems seems to handle its C-state changes far more stably than Penryn (which requires more motherboard intervention), even when the overclock is 50 percent.
http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/ab4-3.jpg (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/ab4-8.jpg) http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/ab7-3.jpg (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/ab7-8.jpg) http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/ab1-3.jpg (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/ab1-8.jpg)
Click to enlarge
BCLK Frequency - 200(MHz): BCLK = Base clock. This affects the QPI and uncore (L3 cache, northbridge) frequency too - some motherboards like the Intel Smackover allow the ratios to be adjusted, but the Asus does not. Here the ratio is 18x for the QPI and 16x for the uncore (northbridge/L3 cache). The uncore frequency must also always be below the QPI, we’re told.
DRAM Frequency - 1,600MHz: Although if you don't have uber-ram, set it to the lower frequency as the bandwidth will still be super-sized regardless.
CPU Voltage - 1.35V: We found this was plenty, depending on your own CPU's needs, it might be happy using less.
CPU PLL Voltage - 1.96V: In all honesty, we've got to play with this function more, but a 0.16-0.2V increase worked for Penryn so we're also using it here.
http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/ab6-3.jpg (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/ab6-8.jpg) http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/ab5-3.jpg (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/ab5-8.jpg) http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/ab2-3.jpg (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/ab2-8.jpg)
Click to enlarge
http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/ab3-3.jpg (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/ab3-8.jpg)QPI/DRAM Voltage - 1.35V: This is poorly worded by Asus - it should read uncore or QPI/memory controller voltage so not to confuse it with the actual memory voltage. Increasing this is also necessary as it helps overclock the base frequency as the uncore area overclocks increase in relation to the CPU core overclocks. This voltage is tied to actual DRAM voltage - the two are directly connected on the motherboard. You'll need to increase this to keep the CPU safe.
While Asus and Intel (rightly) scare everyone (read: uneducated) into thinking that 1.65V on the DRAM voltage should be the absolute limit before you reach for the fire-blanket, all that's really needed it to obey this: keep the CPU uncore voltage within 0.5V difference of the DRAM voltage and there's no problem. Over this potential difference and you’ll greatly increase the chance of CPU death, but it certainly won't happen instantly in a big ball of fail fire if you make a mistake.
DRAM Voltage - 1.66V: This is the closest to the 1.65V the Corsair Dominator DIMMs wanted and it's within the 0.5V Uncore difference.
If you are familiar with Intel systems, the best thing to do is treat QPI frequency like you would Front Side Bus and cranking up the QPI also levies another advantage - increased memory frequencies. Because the Core i7 920 uses the basic 4.8GT/s QPI frequency there is no option available here to adjust it, so you don't have to worry about it, however being able to see what its "final frequency" post-overclock would be incredibly useful.
A little extra differential amplitude because Asus claims in the BIOS that it helps with overclocking and perhaps turning off some unused features like Virtualisation is worth it as well, but keeping the pre-fetchers and HyperThreading on will improve performance.
We found that enabling the HPET (High Performance Event Timer), or as Asus label it, APCI 2, is critical for keeping the clocks on Core i7 CPUs accurate. Without it turned on, the multiplier jumps around crazily if we watch CPU-Z, but with it on, the multiplier reading is solid and the clock frequency only jitters very slightly according to fractional variations in the base clock.
http://www.bit-tech.net/hardware/2008/11/06/overclocking-intel-core-i7-920/3
Manufacturer: Intel (http://www.intel.com/)
We've seen how the "Core" performance lies, but what about stretching the value of a new i7 920 purchase that much more? With an RRP of $284 it’s not exactly a Core 2 Quad Q6600 G0 territory bargain, but it's the cheapest of the new Core i7 CPUs by a large margin.
What potential does $284 buy you though? The Q6600s clocked to between 3.0 and 3.6GHz usually, although inevitably there are some people out there with some serious skills having eked out over 4GHz.
But with a new architecture comes a new way to overclock - we'll walk you through how to get a solid overclock out of the Core i7 920 on two of the latest motherboards, describing what BIOS settings we found worked.
http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/asus1-3.jpg (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/asus1-8.jpg) http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/msi1-3.jpg (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/msi1-8.jpg)
Asus P6T Deluxe and the MSI X58 Eclipse - click to enlarge
Hardware Choices
With the launch of a whole new platform we're currently a little limited when it comes to hardware choices because not everything has arrived at the store-fronts yet. That said, there are two boards we have currently in the office that we’ll try just to see how far both go, although we'll be doing a full review as well so you know the ins and outs in the coming weeks.
In addition to the Core i7 920, we've got the Thermalright Ultra 120 eXtreme 1366-RT and Noctua NH12P with LGA1366 mounting brackets - both offer tremendous cooling power for these 130W TDP CPUs that will be overvolted, increasing their power output.
On the motherboard front we'll be using the MSI X58 Eclipse (http://www.bit-tech.net/hardware/2008/08/26/early-look-msi-x58-eclipse/1) and the Asus P6T Deluxe (http://www.bit-tech.net/hardware/2008/08/21/asus-p6t-deluxe-next-generation-x58-motherb/1) - both of which retail for around £280 here in the UK. Finally we've got a 6GB triple channel Corsair Dominator 2 kit that's rated to 1,600MHz with 8-8-8-24-2T timings at just 1.65V. These should also retail for about $300 (approx. £230) making them an expensive investment.
What's more, because the Core i7 has oodles of memory bandwidth anyway, running triple channel 1,600MHz might not offer the greatest benefits given the price. While we'll investigate how memory bandwidth and latency affects performance specifically in a later article, if we're looking for the most awesome enthusiast platform available, 1,600MHz DDR3 is the way to go at 4GHz simply because it ties in nicely with the Core i7 920 – that’s demonstrated over in the BIOS page.
The rest of the components are identical to those used in the Core i7 review (http://www.bit-tech.net/hardware/2008/11/03/intel-core-i7-920-945-965-review/1) so the results we're quoting here are directly comparable.
Here's how we started out with the Core i7 920...
http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/1-920stocks.png (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/1-920stock.png) http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/2-920stocks.png (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/2-920stock.png) http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/3-920stocks.png (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/3-920stock.png)
We disabled Intel Turbo Mode for these pictures, which causes CPU-Z to read 2.93GHz for the i7 920. Click to enlarge
... and how we ended up after just ten or fifteen minutes of overclocking.
http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/1-4s.png (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/1-4.png) http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/2-4s.png (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/2-4.png) http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/3-4s.png (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/3-4.png)
CPU-Z reads the CAS latency information incorrectly - we had set it at Corsair's specifications of 8-8-8-24-2T in the BIOS. Click to enlarge
Asus P6T Deluxe - Installation
Cracking the board out the box we’re presented with a familiar Asus colour and styled PCB. There are a few new things with the P6T Deluxe we’ve alreadly covered in our early look, and we’ll test them in depth at a later date. However, for those unfamiliar with how to do the basics – here’s a guide to correctly installing a Core i7 CPU, and adding heatsinks and memory to both boards.
http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/b1-3.jpg (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/b1-8.jpg) http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/b2-3.jpg (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/b2-8.jpg) http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/b3-3.jpg (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/b3-8.jpg)
Click to enlarge
The LGA1366 socket is quite a bit different from LGA775, however the seating and mounting mechanism is exactly the same - drop it in (it can only go one way) careful not to displace the tiny pins, then pop the cap over and use the arm to secure it in place. Next, apply some thermal paste over in a thin even spread over the central heatspreader to improve the thermal contact between CPU and heatsink.
http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/b4-3.jpg (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/b4-8.jpg) http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/b5-3.jpg (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/b5-8.jpg) http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/b6-3.jpg (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/b6-8.jpg)
Click to enlarge
Screwing down the new Thermalright Ultra-120 eXtreme-1366 RT is a little tough, but the large springs help create a firmer compression. As the CPU socket itself now has a metal backplate to prevent PCB bending, these high pressure springs should not cause the problem of warping PCBs.
The memory must go in the orange slots first – not the black ones. This is a change to the norm as usually the memory goes into the closest set of memory slots first, but in this case and on the MSI below it’s the set further away.
MSI X58 Eclipse - Installation
To try something different, we've used the Noctua NH-U12P to cool the Core i7 920 on the MSI X58 Eclipse. The CPU is installed in the exact same way as the Asus board, and while the Noctua takes a little extra time to fit the bracket its two sprung screws are far easier to secure than the high pressure ones used on the Thermalright.
http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/msi2-3.jpg (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/msi2-8.jpg) http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/msi3-3.jpg (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/msi3-8.jpg) http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/msi4-3.jpg (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/msi4-8.jpg)
Click to enlarge
Unfortunately this is as far as we got on our early revision 1.1 board. We had set it up, got to know the BIOS a little and overclocked it to 4GHz - matching the Asus - then tried to burn it in a bit with some Prime95. And burn it we did - the board lasted about 30 seconds before one of the memory MOSFETs burnt out in a puff of blue smoke.
We're currently working with MSI to understand why this happened and will update this article in due course. Unfortunately, it's not unusual for early boards off the production line from any manufacturer to either arrive DoA or pop after a short while. We hate to say it but a new batch of a brand new board fresh off the production line occasionally hasn’t got all the manufacturing bugs ironed out. At worst case, MSI has a duff batch of Power-PAK MOSFETs.
We know this having occasionally followed MSI during the board’s design that it’s been tested further than we’ve lightly pushed it here and since we weren’t doing anything untoward it we expect this was simply just a duff part.
Asus P6T Deluxe - BIOS Setup
The Core i7 920 has a 4.8GT/s QPI and a slower northbridge/Uncore frequency than the Core i7 965, which gives it plenty of overhead to dive into. The Core i7 920 CPU is multiplier locked (only the Extreme Edition 965s are unlocked), so we'll have to increase the QPI frequency to get more MHz.
AI Overclock Tuner - Manual: Although if you're lucky enough to have XMP ready memory you might want to try that - 1,600MHz sets the QPI link to 200MHz - just what we needed for 4GHz, but we still did it manually anyway.
Intel Turbo Mode - Disable: We disabled it so as it would not interfere with the overclock, however we left on the new Intel low power states. Normally this affects how the CPU overclocks and in extreme cases we expect it will, because the on/off effect to the CPU frequency and voltages as the C-state changes.
Intel has stopped multiplier dropping its CPUs like it does with Penryn, instead it just turns the clocks and cache off in stages to reduce power of the cores. However considering the CPU has a 130W TDP before overvolting and overclocking, we didn't quite fancy running it all guns blazing all the time (we still need the CPU for future testing!). We found the on-board power microcontroller built into the Nehalems seems to handle its C-state changes far more stably than Penryn (which requires more motherboard intervention), even when the overclock is 50 percent.
http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/ab4-3.jpg (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/ab4-8.jpg) http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/ab7-3.jpg (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/ab7-8.jpg) http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/ab1-3.jpg (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/ab1-8.jpg)
Click to enlarge
BCLK Frequency - 200(MHz): BCLK = Base clock. This affects the QPI and uncore (L3 cache, northbridge) frequency too - some motherboards like the Intel Smackover allow the ratios to be adjusted, but the Asus does not. Here the ratio is 18x for the QPI and 16x for the uncore (northbridge/L3 cache). The uncore frequency must also always be below the QPI, we’re told.
DRAM Frequency - 1,600MHz: Although if you don't have uber-ram, set it to the lower frequency as the bandwidth will still be super-sized regardless.
CPU Voltage - 1.35V: We found this was plenty, depending on your own CPU's needs, it might be happy using less.
CPU PLL Voltage - 1.96V: In all honesty, we've got to play with this function more, but a 0.16-0.2V increase worked for Penryn so we're also using it here.
http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/ab6-3.jpg (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/ab6-8.jpg) http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/ab5-3.jpg (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/ab5-8.jpg) http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/ab2-3.jpg (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/ab2-8.jpg)
Click to enlarge
http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/ab3-3.jpg (http://images.bit-tech.net/content_images/2008/11/overclocking-intel-core-i7-920/ab3-8.jpg)QPI/DRAM Voltage - 1.35V: This is poorly worded by Asus - it should read uncore or QPI/memory controller voltage so not to confuse it with the actual memory voltage. Increasing this is also necessary as it helps overclock the base frequency as the uncore area overclocks increase in relation to the CPU core overclocks. This voltage is tied to actual DRAM voltage - the two are directly connected on the motherboard. You'll need to increase this to keep the CPU safe.
While Asus and Intel (rightly) scare everyone (read: uneducated) into thinking that 1.65V on the DRAM voltage should be the absolute limit before you reach for the fire-blanket, all that's really needed it to obey this: keep the CPU uncore voltage within 0.5V difference of the DRAM voltage and there's no problem. Over this potential difference and you’ll greatly increase the chance of CPU death, but it certainly won't happen instantly in a big ball of fail fire if you make a mistake.
DRAM Voltage - 1.66V: This is the closest to the 1.65V the Corsair Dominator DIMMs wanted and it's within the 0.5V Uncore difference.
If you are familiar with Intel systems, the best thing to do is treat QPI frequency like you would Front Side Bus and cranking up the QPI also levies another advantage - increased memory frequencies. Because the Core i7 920 uses the basic 4.8GT/s QPI frequency there is no option available here to adjust it, so you don't have to worry about it, however being able to see what its "final frequency" post-overclock would be incredibly useful.
A little extra differential amplitude because Asus claims in the BIOS that it helps with overclocking and perhaps turning off some unused features like Virtualisation is worth it as well, but keeping the pre-fetchers and HyperThreading on will improve performance.
We found that enabling the HPET (High Performance Event Timer), or as Asus label it, APCI 2, is critical for keeping the clocks on Core i7 CPUs accurate. Without it turned on, the multiplier jumps around crazily if we watch CPU-Z, but with it on, the multiplier reading is solid and the clock frequency only jitters very slightly according to fractional variations in the base clock.
http://www.bit-tech.net/hardware/2008/11/06/overclocking-intel-core-i7-920/3