Windows Computers Intel i7

Setup

• Intel Core i7 Nahelam 920 2.66 GHz processor [1]
  • Thermalright Ultra-120 extreme cooler [2]
  • Noctua NF-P12 1300 RPM fan [3]
• OCZ DDR3-12800 1600 MHz 8-8-8-24 3 GB (3x1GB) OCZ3G1600LV3GK triple channel memory [4]
• Asus P6T Deluxe Nahelam motherboard [5]
• Seagate Cheetah 15.K6 SAS 15000 RPM 146 GB ST3146356SS hard drive [6]
• Windows XP with Mac OS X Tiger theme and Flyakite OSX look

Nahelam Processor

Nahelam is the name of the new Intel Core i7 processor. It is a 'tock' in the Intel cycle, meaning an architectural change. As opposed to a 'tick' which is a silicon build change.

Quick list of notable changes:

• No more front-side-bus, it's more like AMD with integrated memory controller in the processor
• True quad-core die, not two dual core dies on one processor
• Automatically clock the processor if only one is active
• 45 nm lithography, same as Penryn
• Maximum 1.65 Volt for the DRAM bus/controller
• New socket, 1366 pins, because of the integrated memory controller
• More expensive motherboards, launch boards was around 300USD
• Hyperthreading is back, meaning 2x 4 cores, 8 threads

Motherboard

At launch Intel and Asus were the first to launch their motherboards. I got the Asus P6T Deluxe board for free after I've complete a price guide system for a friend (thanks pibbz).

The P6T is feature packed, it even got a Serial Attached SCSI (SAS) controller.

For a full specification list, check the Asus product page.

Overclocking

This is were it gets exciting. The Nahelam processor is very flexible, meaning it can handle high clock rates. This might have something to do with the fact that it is design to dynamically increase the performance (thus the clock rate) when there are idle cores.

To overclock the system, only a few settings has to be changed:

• BCLK Frequency - Base clock, feeded to the processor, IOH, and ICH chipset, think of this like the old FSB
  • Default 133 MHz
• CPU/Core Voltage - Processore core Voltage
  • Default 0.8 - 1.375V
• Uncore Voltage - Uncore is everything else on the processor (hence the name), meaning the QPI links, L3 cache, and DRAM memory controller. This should reflect the DRAM Voltage and vice versa
  • Default 1.5V, not over 1.65V
• DRAM Frequency - Set this to the specified speed of the memory
  • PC3-8500/1066 MHz PC3-10666/1333 MHz PC3-12800/1600 MHz, or higher
• DRAM Voltage - Memory DIMM Voltage
  • Depends on the memory, normally 1.5V
• Current Limit Override / CPU TM - Disable the Thermal Monitor on the processor to keep it from dropping the processor speed when it it's hitting the thermal ceiling of 130W or 100A.
  • Default enabled

Optionally:

• CPU Ratio - Unlocked only on highest models
• QPI Data Rate - The Quick Path Interconnect bandwidth, ratios are 18x 21x and 24x, times the BCLK, limited at max 4000 MHz (see below)
• Spread Spectrum - Disable, it modulates the frequency of the buses by a few megahertz to avoid a build-up of electro-magnetic interference.
  • Default enabled
• IOH voltage - The X58 controller is responsible for the PCI-E lanes and DMI to the southbridge (think of this as the old Northbridge)
  • Default 1.1V
• ICH voltage - ICH10 Southbridge controller for every peripheral connected to the system
  • Default 1.1V
• IOH PCI-E Voltage - PCI-Express bus Voltage
  • Default 1.50V
• ICH PCI-E Voltage - PCI-Express bus Voltage
  • Default 1.50V
• HPET or APCI 2.0 - Disable or enable the High Performance Event Timer
  • Default Disabled

The processor will draw significant amount of power when all 4 cores are under load. An appropriate powersupply is certainly needed, in the 500-600 watt range with good efficiency. If the system suddenly shuts down and does not reboot automatically, it's a sign of an overloaded PSU.

Another important factor is the thermal cooling, a good third-party CPU cooler is a good investment when overclocking. Remember that the stock speed on a processor and the stock fan that is bundled along is picked to match the heat it will produce. Overclocking it will produce more heat than the fan specified for, thus the overclock will fail/crash at a certain level.

Intel warns against rising the Uncore voltage over 1.65V, but reports says that's not the case if both the DRAM voltage and Uncore voltage is set within 0.5V margin when the voltage is set over the 1.65V limit.

Overclocking is limited by the QPI ratio multiplier which can't be set lower than 18x [7] (supposedly fixed in the processor). When the QPI reaches 4000 MHz (222x18) it hits a wall. An easy way to try this is to set the CPU multiplier to 12x, BCLCK to 222, QPI data rate to 7992MT/S, and memory at their rated specs (1600 MHz/1.65V, 9-9-9-24). When you try to boot with these settings it should work, but once you change the QPI data rate to 21x or 24x (9324MT/S and 10656MT/s respectively), it won't POST because QPI data rate is past 4000MHz (222x18=3996, 222x21=4662, 222x24=5328).

3.8 GHz Stable Overclock

A 190 MHz base clock and 1.47500V core was needed to run the system stable without the "Current Limit Override" (CPU TM) kicking in. The current limiter will decrease the CPU ratio multiplier when the processor exceeds 130W or 100A, mainly a feature that is desired in servers, workstations, and laptops. SuperPI finished a 1M run in 10.984 sec.

Stable:

• CPU Ratio: 20
• BLCLK: 190
• DRAM: 1523 MHz (190x8)
• UCLK: 3047 MHz (190x16)
• QPI Rate: 6857MT/s (190x18x2)
• CPU Voltage: 1.45000
• CPU PLL Voltage: 1.90
• Uncore QPI/DRAM Voltage: 1.35
• DRAM Voltage: 1.64
• DRAM timing: 9-9-9-25
• IOH Voltage: 1.10
• ICH Volrage: 1.10
• Spread spectrum: Disabled
• ACPI 2.0 / HPET: Disabled
• CPU TM: Disabled

4.2 GHz Overclock

This is the highest I could make the system boot Windows XP and complete a SuperPI 1M run (09.812 sec). Temperature hitting the dangerous 70 degrees while idle with stock cooler.

• CPU Ratio: 19
• BLCLK: 220
• DRAM: 1763 MHz (220x8)
• UCLK: 3528 MHz (220x16
• QPI Rate: 10586MT/s (220x24x2)
• CPU Voltage: 1.48750
• CPU PLL Voltage: 2.10
• Uncore QPI/DRAM Voltage: 1.65
• DRAM Voltage: 1.66
• DRAM timing: 10-10-10-25
• IOH Voltage: 1.30
• ICH Volrage: 1.30
• Spread spectrum: Disabled
• ACPI 2.0 / HPET: Disabled

Overclocking References

• custompc.co.uk - Core i7 Overclocking
• i4memory.com - Intel Core i7 920 overclocking (Asus P6T Deluxe)
• tomshardware.com Editor's Corner: Overclocking Core i7
• bit-tech.net Overclocking Intel's Core i7 920
• legionhardware.com - Intel Core i7 2.66 GHz Processor Gaming System
• overclockersclub.com - Asus P6T Deluxe OC Edition Review - Overclocking
• techgage.com - ASUS P6T Deluxe OC Palm Edition - Overclocking
• hexus.net - ASUS P6T how do i overclock thread
• xtremesystems.org - Nehalem Overclocking @ XS thread
• extremesystems.org - ol'norton Core i7 965 Overclocking

Tools

• SuperPi Mod - Quick benchmarking
• CPU-Z - Processor and system details
• Prime95 - Processor stability testing
• Asus AI Suite - Fan control and system details
• Real Temp - Temperature for individual cores
• Core Temp - Alternative temperature monitor

References

• Intel Core i7 (Nehalem): Architecture
• The Dark Knight: Intel's Core i7
• Power management and, uh, forced induction
• Review Tryouts: Thermalright Ultra-120 Extreme
• Noctua NF-P12 120mm fan