ASUS P5E3 Deluxe Overclocking: DDR3 Takes Front Stage
by Kris Boughton on November 20, 2007 4:00 AM EST- Posted in
- CPUs
More BIOS Setup and Tweaking
FSB Termination Voltage: Maximum of 1.50V. Undeniably the Achilles' heel of this fine board, 1.5V (VTT) is simply not enough to carry most 65nm quad-cores above ~500MHz FSB. Most CPUs/MCHs require this voltage to quickly ramp up from the default (1.20V) to near maximum when overclocking from about 450MHz FSB and higher.
DRAM Voltage: Maximum of 2.78V. Base DDR3 voltages are set to 1.5V with most performance kits requiring somewhere between 1.8V and 1.95V. Our recommendation is never to exceed the manufacturer's maximum specified voltage. With that said, values in excess of ~2.2V with DDR3 are a death sentence. In light of this, allowing a voltage as high as 2.78V seems irresponsible but is a required marketing feature.
NB Voltage: Maximum of 1.91V. NB Voltage, also known as VMCH, is an integral part of high-FSB overclocking, especially when running a "boosted" Ai Transaction Booster level. Maximum FSB achieved with a 65nm quad-core was around ~1.75V VMCH. Voltages above 1.75V, being excessive, will more than likely accelerate the failure of your board and cause unneeded heating of the MCH die.
Certain instabilities arose when running Northbridge voltages in excess of ~1.75V, caused by high internal die temperatures because of the voltage. Simply lowering VMCH was enough to return to stable operation. We've also found that the X38 chipset is far more sensitive to heat than any other Intel chipset to date. In fact, the BIOS is kind enough to warn the inexperienced user that Northbridge voltages in excess of 1.75V require a more effective cooling solution as the stock heatsink and heatpipe assembly can only do so much.
SB Voltage: Maximum of 1.20V. Some users have claimed that a higher Southbridge voltage provides for additional stability when running the PCI-E frequency out of specification. We have found leaving this voltage on Auto as the most appropriate solution, even when overclocking.
Clock Over-Charging Voltage: Maximum of 1.00V. Phase change, dry ice (DI) and liquid nitrogen (LN2) benchers may find higher settings here useful when cooling the CPU and surrounding area down to very low levels. All others would do best to leave this on Auto.
Load-Line Calibration: Acts to reduce the affects of VDroop during periods of heavy CPU loading. Enabling Load-Line Calibration may allow you to set a lower CPU Voltage in the BIOS while retaining overall system stability.
CPU/NB GTL Voltage Reference: CPU: Auto, 0.63x, 0.61x, 0.59x, and 0.57x. NB: Auto, 0.67x, and 0.61x. CPU Gunning Transceiver Logic (GTL) voltages are nothing more than reference levels that the CPU uses when determining if a data or address signal is either high (1) or low (0). Precision voltage dividers generate these voltages and are usually specified as a percentage of VTT. In the case of 0.67, this would be 67% of VTT. For example, if VTT is 1.20v then a CPU GTL Voltage Reference of 0.67x would result in a GTLREF value of 0.67 x 1.20V = ~0.80V.
These reference values are particularly important when overclocking quad-core CPUs, especially when venturing above about 450FSB. The ability to tune these values per die can mean the difference between 475FSB and 500FSB. Unfortunately, ASUS' implementation of this functionality is rather incomplete as manipulation of only a single GTLREF value is possible (and in a somewhat imprecise manner). The real power in GTLREF tuning comes in the ability to provide each quad-core die with separate reference values. (Recall that current quad-cores are an MCM consisting of two dual-core dies on a single package.) Unfortunately, this is not a matter of future BIOS modification as providing two distinct voltages to separate pins on the CPU would require nothing less than a PCB revision. As such, this board will most likely never see its full potential when clocking quad-core CPUs but it still performs admirably.
This same information applies to the NB GTL Voltage Reference setting except that there is no need for more than one reference value. In the case of each, we would like to see much finer control of these values. Ironically, the board's controllable voltages that need the least amount of precision seem to have the most. However, ASUS is working on these requests for their next boards; in the meantime, unless you push the board past about 98% of its maximum, these shortcomings will not affect the typical user of this board. We might add that other manufacturers face the same problem.
CPU/PCIE Spread Spectrum: Set both to Disabled for a more stable clocking signal.
FSB Termination Voltage: Maximum of 1.50V. Undeniably the Achilles' heel of this fine board, 1.5V (VTT) is simply not enough to carry most 65nm quad-cores above ~500MHz FSB. Most CPUs/MCHs require this voltage to quickly ramp up from the default (1.20V) to near maximum when overclocking from about 450MHz FSB and higher.
DRAM Voltage: Maximum of 2.78V. Base DDR3 voltages are set to 1.5V with most performance kits requiring somewhere between 1.8V and 1.95V. Our recommendation is never to exceed the manufacturer's maximum specified voltage. With that said, values in excess of ~2.2V with DDR3 are a death sentence. In light of this, allowing a voltage as high as 2.78V seems irresponsible but is a required marketing feature.
NB Voltage: Maximum of 1.91V. NB Voltage, also known as VMCH, is an integral part of high-FSB overclocking, especially when running a "boosted" Ai Transaction Booster level. Maximum FSB achieved with a 65nm quad-core was around ~1.75V VMCH. Voltages above 1.75V, being excessive, will more than likely accelerate the failure of your board and cause unneeded heating of the MCH die.
Certain instabilities arose when running Northbridge voltages in excess of ~1.75V, caused by high internal die temperatures because of the voltage. Simply lowering VMCH was enough to return to stable operation. We've also found that the X38 chipset is far more sensitive to heat than any other Intel chipset to date. In fact, the BIOS is kind enough to warn the inexperienced user that Northbridge voltages in excess of 1.75V require a more effective cooling solution as the stock heatsink and heatpipe assembly can only do so much.
SB Voltage: Maximum of 1.20V. Some users have claimed that a higher Southbridge voltage provides for additional stability when running the PCI-E frequency out of specification. We have found leaving this voltage on Auto as the most appropriate solution, even when overclocking.
Clock Over-Charging Voltage: Maximum of 1.00V. Phase change, dry ice (DI) and liquid nitrogen (LN2) benchers may find higher settings here useful when cooling the CPU and surrounding area down to very low levels. All others would do best to leave this on Auto.
Load-Line Calibration: Acts to reduce the affects of VDroop during periods of heavy CPU loading. Enabling Load-Line Calibration may allow you to set a lower CPU Voltage in the BIOS while retaining overall system stability.
CPU/NB GTL Voltage Reference: CPU: Auto, 0.63x, 0.61x, 0.59x, and 0.57x. NB: Auto, 0.67x, and 0.61x. CPU Gunning Transceiver Logic (GTL) voltages are nothing more than reference levels that the CPU uses when determining if a data or address signal is either high (1) or low (0). Precision voltage dividers generate these voltages and are usually specified as a percentage of VTT. In the case of 0.67, this would be 67% of VTT. For example, if VTT is 1.20v then a CPU GTL Voltage Reference of 0.67x would result in a GTLREF value of 0.67 x 1.20V = ~0.80V.
These reference values are particularly important when overclocking quad-core CPUs, especially when venturing above about 450FSB. The ability to tune these values per die can mean the difference between 475FSB and 500FSB. Unfortunately, ASUS' implementation of this functionality is rather incomplete as manipulation of only a single GTLREF value is possible (and in a somewhat imprecise manner). The real power in GTLREF tuning comes in the ability to provide each quad-core die with separate reference values. (Recall that current quad-cores are an MCM consisting of two dual-core dies on a single package.) Unfortunately, this is not a matter of future BIOS modification as providing two distinct voltages to separate pins on the CPU would require nothing less than a PCB revision. As such, this board will most likely never see its full potential when clocking quad-core CPUs but it still performs admirably.
This same information applies to the NB GTL Voltage Reference setting except that there is no need for more than one reference value. In the case of each, we would like to see much finer control of these values. Ironically, the board's controllable voltages that need the least amount of precision seem to have the most. However, ASUS is working on these requests for their next boards; in the meantime, unless you push the board past about 98% of its maximum, these shortcomings will not affect the typical user of this board. We might add that other manufacturers face the same problem.
CPU/PCIE Spread Spectrum: Set both to Disabled for a more stable clocking signal.
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Owls - Tuesday, November 20, 2007 - link
DDR2 is hardly "inferior". When comparing 4GB of DDR3 vs 4GB of DDR2, I can build a whole new computer with what I'd have spent on DDR3. It just doesn't make sense right now no matter how you cut it.. and only having 1GB of ram now?TA152H - Tuesday, November 20, 2007 - link
I run most of my machines with 512 MB, so 1 GB is hardly a problem.There are some things you need more memory than 1 GB for.
When I see stuff like "It doesn't make sense no matter how you cut it", I instantly think you're an idiot. You're probably not, but that statement is absurd. There is always a group that the cost of the most expensive, and fastest parts, makes sense. The cost of memory is trivial compared to the cost of salaries, for example, and spending $500 to help someone work faster pays for itself very quickly.
I think the main problem is that most people do not understand that more memory does not always make things faster. I deal with this all the time.
AnnihilatorX - Tuesday, November 20, 2007 - link
Correct me if I am wrongThe increase in FPS you see going from 400x9 to 465x9 is nearly 100% due to increase in CPU frequency
The performance increase of a 465x9 RAM running at 2:1 memory divider would be less than 5% higher than a similar configuration of 465x9 with slower RAM running at lower divider ratios.
That would mean there is no sense to buy a premium DDR3 for $500 extra for what you can do with less than 5% performance sacrifice with the dirt cheap DDR2 RAM.
snarfbot - Sunday, November 25, 2007 - link
no everything you said is correct.the thing that really gets me though, is that pc6400 ddr2 is commonly capable of reaching 485mhz at lower timings. so whats so great about ddr3?
on a p35 you can easily reach the same speed with cheap memory, at cas 5, sometimes even cas 4 with good overclockable ram.
so basically the only benefit that ddr3 has going for it is the lower voltage required, and of course lower temps, not worth the premium. period.
Aivas47a - Tuesday, November 20, 2007 - link
This is one of the best, detailed overclocking guides I've ever seen. Excellent job! I'm especially glad to have the mystery of Transaction Booster, Skew, and Clock Twister in the Asus bios explained.Now, if you guys could just prepare a guide for memory subtimings, the treatise would be complete. :)
Thanks very much for this.