AMD FX Processors Unleashed | a Guide to Performance Tuning with AMD OverDrive and the new AMD FX Processors
Disclaimer The information presented in this document is for informational purposes only and may contain technical inaccuracies, omissions and typographical errors.
Introduction Systems based on the platform technology codenamed “Scorpius” may be tuned to deliver added system performance. The AMD FX™ CPUs and the AMD 9-series chipset motherboards offer an exciting amount of performance tuning options, including potential overclocking headroom. Note that each processor and chipset is different, and may result in lower or no overclocking margin. The critically acclaimed AMD OverDrive™ utility gives users advanced control of system performance.
Glossary of Terms HyperTransport™ Reference Clock (HT ref. clk): The base clock for various clock domains on the AMD “Scorpius” platform technology. HT ref. clock is 200MHz by default. CPU, CPU NB, HT Link and Memory clocks are all linked to HT ref. clock. HT ref. clock adjustment is a good tool for fine tuning the various clocks to optimal values. The HT ref. clock value itself doesn’t have any impact on performance. CPU: Central Processing Unit – the engine of the AMD “Scorpius” platform technology.
Glossary of Terms – continued CPU / CPU NB Voltage OFFSET: Most AMD “Scorpius” platform technology motherboards have a BIOS option that allows Voltage adjustments beyond the CPU VID Voltage range. This voltage offset is added on top of the VID value. Voltage offset could be negative or positive. Actual voltage level = CPU or CPU NB VID + OFFSET. Example: VID 1.350V + 0.100V OFFSET = 1.450V actual voltage level.
AMD OverDrive™ utility The AMD OverDrive™ utility is a comprehensive utility for performance tuning, system monitoring and testing. PLEASE NOTE THAT THE AMD PRODUCT WARRANTY DOES NOT COVER DAMAGES CAUSED BY RUNNING COMPONENTS OUTSIDE OF SPECIFICATION. Download from AMD Game! Website - http://sites.amd.com/us/game/downloads/amd-overdrive/Pages/overview.aspx Advanced Mode The AMD OverDrive utility is a powerful tool with numerous features and options.
Figure 1, presented above shows all the available clock/voltage tuning options available in the AMD OverDrive™ utility. The processor, northbridge, PCIe and memory can all be adjusted to obtain an optimally tuned system. Detailed description of Figure 1 (AMD OverDrive utility screenshot): Current clock speeds (1) PCIe® Speed (5) This section offers real-time monitoring for all the crucial clock speeds This item controls the PCIe® clock frequency of the PCIe® graphics slots.
Memory Tuning 1 2 Figure2: AMD OverDrive™ utility Memory Tuning Memory timing adjustments (1) Memory Drive strength control (2) The items circled with red color can directly affect the overall system performance. Reducing these values can improve the performance / lower memory clock tuning margin whereas using higher values can enable higher memory clock speeds (but lower clock-to-clock performance). The lower half of the Memory tuning screen includes various Drive Strength control items.
AMD OverDrive™ utility Stability Test The AMD OverDrive™ utility features an impressive system stability assessment. The “Stability Test” tab under “Performance Control” incorporates AMD’s CPU test algorithms to stress the CPUs worst-case scenario. The test consists of various parts that can be set to run only on a specific CPU core or on all CPU cores. It is also possible to select only specific tests to run. The amount of time the test will run can also be adjusted with the slider.
AMD “Scorpius” platform – Performance Tuning Suggestions CPU Core Clock Performance Tuning CPU core clock is the most important item to adjust for the advanced users when tuning the performance of the system. The CPU Clock speed has a big impact on overall system performance. The following steps explain how to determine the CPU tuning margin.
The key settings in the Windows® XP, Windows Vista® or Windows 7® operating system to adjust before overclocking the CPU: • • • Close all major applications and background tools and save any open documents Set OS to “High performance” mode via “Control Panel / Power Options” Close any third party hardware / clock monitoring and system information programs CPU tuning with the AMD OverDrive™ utility: PLEASE NOTE THAT THE AMD PRODUCT WARRANTY DOES NOT COVER DAMAGES CAUSED BY RUNNING COMPONENTS OUTSIDE OF SPE
CPU NorthBridge Performance Tuning The CPU NorthBridge (CPU NB) clock speed determines the efficiency and bandwidth capacity of the Memory controller. L3 cache runs at this frequency as well. CPU NB performance tuning gives a measurable boost for overall system performance. In particular it can reduce the Memory latency and improve L3 cache bandwidth and latency. In some scenarios the CPU NB should be tuned in order to take the full advantage of overclocked Memory frequency and bandwidth.
Figure 7: AMD OverDrive™ utility HT ref. clock slider 5) Run a stability test before increasing the HT ref. clock to another level 6) Adjust CPU NB VID voltage slider in AOD if there were any stability issues (in 0.050V steps – the AMD FX-8150 CPU may require 1.300…1.375V CPU NB Voltage to reach the full performance tuning potential on air/watercooling) a.
CPU NB performance tuning through the BIOS menu: 1) Set the CPU NB clock speed up to the next available value (example: if 1800MHz / x9 is the default and NB clock testing via AMD OverDrive utility was OK at 2000MHz then set CPU NB BIOS item to 2000MHz / x10 now) 2) Set CPU NB Voltage to a known stable value (based on the NB clock testing done thru AMD OverDrive utility) 3) Keep HT Link multiplier at default value or lower it by one step (example: 2400MHz or x12 in the case of the AMD FX-8150 CPU) 4) Set CP
Memory Performance tuning – AM3+ / DDR3 PLEASE NOTE THAT THE AMD PRODUCT WARRANTY DOES NOT COVER DAMAGES CAUSED BY RUNNING COMPONENTS OUTSIDE OF SPECIFICATION INCLUDING DAMAGES CAUSED BY OVERCLOCKING (EVEN WHEN OVERCLOCKING IS ENABLED WITH THE AMD OVERDRIVE UTILITY). Memory clock speed is tied to HT ref. clock with certain ratios.
Advanced Memory tuning examples: The following BIOS settings may improve the Memory performance tuning margin and enable operation at the higher memory clock modes (DDR3-1866…2400).
Figure 10: Example settings for DDR3-2133 memory clock mode (2 DIMMs, one DIMM per channel) The following memory timing fine tune parameters that may further improve the clock margins and/or stability: Figure 11: Memory clock fine tuning parameters NOTE: “Address/CMD Setup Time” & “Address/CMD Fine Delay” –parameters may also be set to “0” 17
HyperTransport™ (HT) reference clock HT reference clock value has no direct impact on system performance. Therefore the maximum amount of HT reference clock tuning is not required in order to get the highest performance. HT ref. clock can be used to fine tune and dial in the other key clock values on the AMD “Scorpius” platform technology. In some cases a relatively high (over 250MHz) HT reference clock might be required for optimal performance.
AMD “Scorpius” Platform Technology – Performance Tuning Targets The following table lists some possible results for an unlocked AMD FX-8150 CPU as well as the optimal voltage values for most AMD “Scorpius” platform technology systems. Note that these results are strictly estimates based on overclocking data from a limited sample size. The actual results will vary depending on the CPU, motherboard, cooling solution and memory modules used in the tests.
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