Core 2 Quad Q8200 O/C Performance And Efficiency

by Thomas Soderstrom

Intel Quad-Core Test Settings
	Default Settings	Overclock Settings
CPU	Intel Core 2 Quad Q8200 2.33 GHz 4 MB L2 Cache, 1.16V	2.69 GHz, (7x 384 MHz) 1.29V core, 1.40V FSB
RAM	DDR3-1333 CAS 9-9-9-24, 1.50V	DDR3-1536 CAS 6-6-5-16, 1.65V
Motherboard	MSI P45 Diamond LGA-1366, P45/ICH10R, BIOS 1.5 (10/10/2009)
Graphics	Zotac GeForce GTX260² 576MHz GPU, 999 MHz Shader, 896MB GDDR3-2484
Hard Drive	Western Digital VelociRaptor WD30000HLFS 300 MB, 10,000 RPM, 16 MB Cache
Sound	Integrated HD Audio
Networking	Integrated Gigabit LAN
Software
Operating System	Microsoft Windows Vista Ultimate x64 SP1
Graphics	GeForce 182.08 Desktop

A stock FSB clock that was already near the processor’s limit made this the most disappointing overclocking experience we can remember since National Semiconductor’s Cyrix MII. Its measly 15% gain felt like a tremendous achievement, however, considering the great effort required to reach a 2.69 GHz clock frequency.

Sandra Arithmetic and Multimedia show CPU performance gains of 14 to 15 percent.

A memory bandwidth increase of 19% looks much better, but isn’t as noteworthy in a CPU overclocking guide.

Low core voltage plus high FSB voltage brings a significant penalty in power consumption, even though performance gains were mediocre at best.

An efficiency loss of 9% results from a ratio of performance to power consumption for the overclocked configuration.

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Overclocking Intel's Core 2 Quad Q8200

by Thomas Soderstrom

Intel’s value-priced Core 2 Quad Q8200 uses two of the same processor dice as the Pentium E5200, at a lower clock speed and a higher front side bus clock. The combination of moderate CPU frequency and higher FSB also requires a lower CPU multiplier, and Intel designs these so that the multiplier cannot be increased.

Intel typically uses a low FSB on mainstream processors to modulate performance and expand compatibility, so we’re not certain why the company chose FSB-1333 for its cheapest quad-core models. We do, however, know that many overclockers specifically select low-cost processors for the higher multiplier that typically accompanies a lower bus speed, so that its use of FSB-1333 for the Q8000-series has all but prevented its adoption amongst enthusiasts. After looking at the far higher prices of Q9000-series processors, we returned resolute to get big gains from the Q8200, viewing its lower multiplier as a challenge.

Unfortunately, the Q8200 would barely budge beyond its original 2.33 GHz frequency, regardless of how much voltage we applied to its core, reaching the same 2.5 GHz overclocked speed at core voltage settings from stock to 1.45 volts. The problem, it seems, is that FSB-1333 is almost the limit for these cores at stock FSB voltage.

Dual-die processors of this design use the front side bus for both CPU-to-chipset and die-to-die communication, and increasing the CPU FSB beyond 354 MHz (2.5 GHz CPU clock) would require an increase of the “VTT FSB Voltage” setting seen in the second screenshot below.

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Our research showed that CPU FSB voltage had the same practical limit as core voltage: 1.45 volts peak and “something less” under load for continuous long-term use. As with the core voltage of the E5200, we chose 1.40 volts as a target voltage for Q8200’s FSB. We were then able to increase the FSB to 384 MHz, but the resulting 15% overclock is barely worth the risk and effort.

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We really wanted to reach at least the next “Intel standard” FSB clock of 400 MHz, or FSB-1600, but getting there required far more “VTT FSB Voltage” than we can safely recommend. Further research into other far-more-successful Q8200 overclocks revealed that those units were actually cream-of-the-crop “Q8200S” models.

The CPU cores certainly wouldn’t need a full 1.40 volts at so low an overclock, so we began back-tracking. While “VTT FSB Voltage” remained at 1.40 volts for a stable 384 MHz FSB, we were able to drop the “CPU Voltage” setting to 1.30 volts. Anything less resulted in an eventual crash under Prime95 v25.8 build 4.

With the chipset’s maximum memory clock rate of twice the CPU FSB clock, the fastest selectable memory clock of 768 MHz provided a data rate of DDR3-1536. As with the E5200, we then began stability tests using Memtest86+ v1.70 at progressively lower DRAM latency settings until the best stable timings of 6-6-5-16 were determined.

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Pentium E5200 O/C Performance And Efficiency

by Thomas Soderstrom

Intel Dual-Core Test Settings
	Default Settings	Overclock Settings
CPU	Intel Pentium E5200 2.50 GHz 2 MB L2 Cache, 1.26V	4.11 GHz, (12x 342 MHz), 1.40V
RAM	DDR3-800 CAS 6-6-6-15, 1.50V	DDR3-1368 CAS 5-5-5-12, 1.65V
Motherboard	MSI P45 Diamond LGA-775, P45/ICH10R, BIOS 1.5 (10/10/2009)
Graphics	Zotac GeForce GTX260² 576MHz GPU, 999 MHz Shader, 896MB GDDR3-2484
Hard Drive	Western Digital VelociRaptor WD30000HLFS 300 MB, 10,000 RPM, 16 MB Cache
Sound	Integrated HD Audio
Networking	Integrated Gigabit LAN
Software
Operating System	Microsoft Windows Vista Ultimate x64 SP1
Graphics	Forceware 182.08 Desktop

A CPU overclock of 64% yielded Sandra Arithmetic and Multimedia benchmark improvements of 63% and 64%, respectively.

Optimized memory settings resulted in a Sandra Memory Bandwidth improvement of 77% over default values.

At 1.40 volts, the overclocked Pentium E5200 required an average 34% power increase.

A performance increase of 64% with an average power increase of 34% allowed the overclocked E5200 to improve its efficiency by 22% over stock settings.

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Overclocking Intel's Pentium E5200

by Thomas Soderstrom

As with AMD, Intel’s production technology already has well-known voltage limits affecting the majority of samples. For 45 nm processors based on the Core 2 architecture, CPU core voltage of 1.45 V is generally considered to be the maximum a processor can withstand over a period of many weeks or a few months. We’ve already seen an “office” system that was overclocked using 1.45 volts lose much of its overclocking capability over a period of around three months. This family of processors continues to scale well, even at much higher voltage levels, but cooling and longevity become an issue.

Because we want our overclocks to last at least several months (and we keep our fingers crossed for 1-3 years of reliable service), we chose 1.40 volts as a target setting under full CPU load and 1.43 volts peak under no load. Knowing the desired voltage level ahead of time negated the normal practice of increasing voltage in small steps until the system became stable after reaching a clock rate that would have otherwise been unstable.

The screenshots below show our final settings: P45 Diamond users must be forewarned that this memory setting required a jumper change which we’ll discuss further down this page.

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Except for its Extreme Edition models, Intel doesn’t allow adjusting its CPU multipliers upward. Using a 12.5x multiplier and 200 MHz FSB clock (FSB-800 via QDR technology), the only way this 2.50 GHz CPU would go faster would be to set a higher FSB. Knowing that the Pentium E5200 should reach at least 3.60 GHz with air cooling, we first tried the next-higher Intel-standard FSB of 266 MHz (FSB-1066). The system booted normally and passed a 40-minute stress test using Prime95 v25.8 build 4. CPU-Z reported core voltage dropping to 1.38V under load however, so we increased the BIOS setting “CPU Voltage (V)” (second screenshot above) to 1.4132 volts. This resulted in 1.424 volts at idle and 1.408 volts at full load.

The MSI P45 Diamond supports most FSB clock settings, but we knew that the chipset would be most stable at or near one of Intel’s standard bus speeds. Our next attempt, FSB-1333 (333 MHz clock) would boot inconsistently, resulting in either a black screen or a system reset following the POST screen. After finding success at 320 MHz “most of the time,” we began to believe that our previous memory ratio problem was being caused by a dreaded bootstrap issue.

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The P45 Diamond doesn’t have “bootstrap” settings in BIOS but does have two jumpers for altering detected bus speed. According to the manual, changing both jumpers from pins 1-2 to pins 2-3 would allow a 200 MHz FSB processor to be detected as a 333 MHz FSB version. Following those instructions solved both the memory ratio and boot inconsistency problems.

The system now booted at 333 MHz, but extended stability tests proved it wasn’t completely stable. In an effort to keep the system close to the 333 MHz “Intel standard” bus, we dropped the CPU multiplier to 12x.

The CPU clock of 12 x 333 MHz proved stable for a longer one-hour Prime 95 test. Jumping ahead slightly, 338 MHz was also stable. We continued increasing FSB and testing stability until it was found that the highest stable CPU speed was 4.1 GHz at 12 x 342 MHz FSB.

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Using our memory manufacturer’s rated setting of 1.65 volts, we began chasing good memory performance to match that impressive 64% CPU overclock. Intel’s DRAM multiplier limit of 2 x FSB clock unfortunately meant that our RAM could be set no higher than a 684 MHz clock, corresponding to a data rate of DDR3-1368.

We began testing lower memory latency values to improve response time, using a bootable CD version of Memtest86+ v1.70 in the same manner that Prime95 was used for CPU stability testing. Since the memory controller is part of the northbridge, we experimented with increased “MCH Voltage” (second screenshot above) until it was found that anything higher than 1.352 volts provided no further improvement.

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Phenom II X2 550 O/C Performance And Efficiency

by Thomas Soderstrom

AMD Phenom II X2 Test Settings
	Default Settings	Overclock Settings
CPU	AMD Phenom II X2 550 3.1 GHz 1MB L2+6MB L3 Cache, 1.288V	3.94 GHz (19.5x 202 MHz), 1.50V
RAM	DDR3-1333 CAS 9-9-9-24, 1.50V	DDR3-1616 CAS 6-6-5-18, 1.65V
Motherboard	MSI 790FX-GD70 Socket AM3, 790FX/SB750, BIOS 1.3 (04/27/2009)
Graphics	Zotac GeForce GTX260² 576MHz GPU, 999 MHz Shader, 896MB GDDR3-2484
Hard Drive	Western Digital VelociRaptor WD30000HLFS 300 MB, 10,000 RPM, 16 MB Cache
Sound	Integrated HD Audio
Networking	Integrated Gigabit LAN
Software
Operating System	Microsoft Windows Vista Ultimate x64 SP1
Graphics	GeForce 182.08 Desktop

A clock speed increase of 27% won’t surprise many experienced overclockers, but the Phenom II X2 550 started out at a fairly high 3.10 GHz. Its final clock rate of 3.94 GHz is fairly impressive for an AMD processor, even though the percent-gained is not. Does this increase translate directly into CPU performance?

CPU Arithmetic performance improved by 25%, while Multimedia extensions performance increased by 26%. The small difference between frequency improvement and performance improvement can likely be attributed to our use of a near-stock HT clock, as described on this guide’s previous page.

Our efforts to reduce memory timings using the processor’s highest memory ratio resulted in a tiny 8% gain in memory performance.

Average power consumption increased by 33%, mostly because of the increased CPU core voltage.

An average CPU performance increase of 26% at an average power increase of 33% yields an average efficiency decrease of around 5%. Overclockers looking for improved efficiency can instead choose a lower core voltage, as overclocking at stock voltage, though limited in performance gain, usually increases efficiency.

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Overclocking AMD's Phenom II X2 550

by Thomas Soderstrom

We follow the overclocking scene fairly closely and have found several overclockers using AMD’s 45 nm processors at voltage levels between 1.50 and 1.56 volts since the Deneb quad-core was first introduced last winter. This level of voltage tolerance is far greater than that of competing Intel models, but to play it safe we chose a maximum setting of 1.50 volts (give or take a few millivolts) under full CPU load, mindful to keep peak unloaded voltage below 1.55 volts.

AMD publishes overclocking software under its “AMD OverDrive Utility” name that allows many of the most important settings to be changed inside Windows. While these can prove useful for finding the processor’s operational limits, many users will eventually want to make these adjustments semi-permanent through BIOS settings.

The traditional overclocking method is to increase clock speed and test for stability, in small steps, until it’s no longer stable. Then increase voltage slightly to make it stable, and repeat until either a thermal limit (too hot) or clock ceiling (where more voltage doesn’t help) is reached. But a little research on the Phenom II X2 550 showed that most samples continue to scale upwards at voltage levels beyond our desired limit. Because of this, we started with our target voltage and attempted to find the highest stable speed it would run at that voltage. The following BIOS images show the results of our efforts, so let’s discuss how we arrived at each setting.

The stock X2 550 clock speed of 3.10 GHz is attained by multiplying the HT clock of 200 MHz by 15.5. MSI's BIOS lists the HT clock as "CPU FSB frequency", though a technical inaccuracy, as AMD insists HT is not an FSB. Since this is a Black Edition processor, most of our overclocking efforts will focus on raising its 15.5x multiplier.

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In MSI's BIOS, “CPU VDD Voltage” refers to the base voltage at which the processor is supposed to be detected, while the “CPU Voltage” setting acts as a type of fine-tuning for load voltage. We started with “CPU VDD Voltage” set to 1.50 volts and “DRAM Voltage” set to the memory manufacturer’s recommended 1.65 volts. The CPU multiplier, listed in the BIOS as “Adjust CPU Ratio,” was then increased to 16x.

We use Prime95 for stability testing, and find it handy that v25.8 build 4 (64-bit Window version) allows every core to be tested simultaneously from one application launch. A launch menu offers several types of tests. The “Small FFTs” option allows full CPU stress without much DRAM testing.

After around 20 minutes of load, we rebooted and increased the CPU multiplier to 16.5x, retested with Prime95, and continued this pattern until the system crashed at 18.5x. Detection program CPU-Z reported that the core voltage was dropping to 1.48 volts, so we went back into the BIOS and increased the “CPU Voltage” setting by 0.20 V (to 1.520 volts) as compensation.

Upon rebooting, the 18.5x setting was found to be Prime95-stable, so we continued making 0.5x increases until the system again crashed at the 21x BIOS setting.

Since we had already reached our target voltage, we tried dropping “Adjust CPU Ratio” in BIOS to 20.5x and let the stability test run longer. After around 45 minutes, the system again crashed. The same was true at a BIOS setting of 20x.

At a BIOS “Adjust CPU Ratio” setting of 19.5x, the system ran stable for several hours. Knowing that we could reach 19.5 x 200 but not 20 x 200, we began increasing the HyperTransport clock, which is the “200” part of 19.5 x 200. Using “Adjust CPU FSB Frequency (MHz)” in the MSI BIOS, we tried an HT clock of 202 MHz with great stability over a one hour test. We then tried 204 MHz and found the system crashed in around 45 minutes. At 203 MHz, the system crashed at around one hour of Prime95 test time, so we reverted back to 202 MHz and again found stability.

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Though it also allows some overclocking adjustments, we used “AMD OverDrive Utility” primarily as a temperature monitor throughout testing. Note that its voltage monitor corresponds to the MSI BIOS' “CPU VDD Voltage” setting, not its “CPU Voltage” setting.

Note to non Black Edition CPU owners: Overclocking an AMD processor that doesn't allow multiplier increases requires raising the HT clock by a far greater amount. The higher data rate will eventually overwhelm the processor's internal HT link, but using the "Adjust CPU-NB Ratio" setting in BIOS to reduce the data multiplier can help. We generally try to keep the HT link data rate (listed below the adjustable setting in MSI BIOS) within 5% of its original speed when overclocking a "locked" AMD processor.

Though this isn’t a memory overclocking guide, we did want to optimize our modules for performance. Our Kingston RAM is rated at DDR3-2000, but the highest DRAM external clock rate available from AMD is four-times the CPU's HT clock. With a HT clock at 202 MHz, this corresponds to a DRAM external clock of 808 MHz and a DRAM data rate of 1616 MHz (see “FSB/DRAM Ratio” in the first BIOS screenshot above).

While the “DRAM Voltage” in the second screenshot above was set to the manufacturer’s recommended 1.65 volts, added stability can often be found by increasing memory controller voltage (“CPU DDR-PHY Voltage” in the same screenshot). With our DRAM data rate limited to 1,616 MHz, we used this added stability to enable lower latency, or wait time between operations, with our modules.

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Starting at our memory’s DDR3-1866-rated CL-tRCD-tRP-tRAS timings of 8-8-8-20, we followed the same method as used for CPU overclocking to decrease each setting until the lowest stable timings were found. A bootable CD version of Memtest86+ v1.70 was used following each setting change for stability testing.

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More Shared Hardware

by Thomas Soderstrom

Though processor families must be used with specific types of motherboards, other parts, such as the power supply, RAM, and hard drive work across multiple platforms.

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Cooler Master’s RS850-EMBA power supply has far more capacity than needed for today’s guide, but was chosen because it was already on the bench. Its 80 PLUS rating should allow realistic comparisons of power draw between stock and overclocked speeds of each processor.

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We didn’t need three modules to test this guide’s dual-channel systems, but two of the same parts can be used in dual-channel mode. Kingston’s DDR3-2000 wasn’t just handy; it’s also capable of low latencies at various speeds, available in single-module packages for dual-channel kits, energy efficient, and able to extract peak performance from each processor. Builders should look forward to a cost-conscious comparison of modern dual-channel kits later this month.

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Western Digital’s VelociRaptor was again chosen for convenience, since its higher-than-average data rate allows quicker load times, but with little to no affect on most benchmark scores. It certainly won’t affect the outcome of today’s overclocks.

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Keeping It Cool

by Thomas Soderstrom

Cool processors clock higher and survive longer, but finding an inexpensive cooler in the preferred 120mm tower design able to support both AMD and Intel processors isn’t easy. Rosewill surprised us with a review sample that included an AMD-style clip, since its Fort 120 doesn’t advertise Socket AM2+/AM3 compatibility on the box. Readers should look forward to a review of this unit later this month.

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This is the point where some die-hard overclockers might point out that, since we used top-end motherboards, we should also use a top-end liquid cooling system. But while budget overclockers might be able to find less expensive motherboards that replicates our results, the same cannot be said of liquid cooling. We wanted to provide a realistic, yet optimistic target for value-overclockers to use as a goal.

One other place we didn’t go cheap was in thermal compound selection. The Fort 120 cooler does not include enough thermal paste for multiple uses, so we instead relied on our established thermal grease choice.

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Zalman’s ZM-STG1 was chosen for previous reviews based on its easy application, quick set in time, and upper-range thermal performance. Upon request, the firm supplied enough samples for each U.S. editor to have two bottles.

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Thermal grease or paste fills small gaps between the processor and heat sink to provide a greater contact area. Many experienced builders swear that too heavy a layer will prevent proper sink contact, citing the lower conductivity of thermal compound compared to the aluminum or copper surface it fills, but most modern thermal materials are thin enough that heat sink pressure will squeeze out any excess. The real problem of applying too much paste is that it can make a mess of the motherboard, and its low-conductivity is still enough to potentially cause signal or voltage problems.

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