Test Setup / Methodology
The 990FX motherboard that we will be using today is ASUS's top of the line Republic of Gamers Crosshair V Formula which we reviewed earlier this year.
- CPU: AMD FX-8150 8-core/8 thread processor (3.6GHz to 4.2GHz, Turbo and C&Q/C1/C6 states on)
- Motherboard: ASUS ROG Crosshair V Formula (BETA 9905 bios made by Shamino - with latest BD AGESA, also unlocks higher memory multipliers)
- RAMs: 2 x 4GB G.Skills RipJawsX 1600Mhz 9-9-9-28 1T (memory frequency/timings investigation later today)
- Graphics: AMD Radeon 6990 (Crossfire) with Catalyst 11.10 Preview 2 (8.901.2.0)
- HSF: Thermalright Silver Arrow with 2 Fans
- SSD: Corsair X128 SSD
- PSU: CM Silent Pro M 1000W
- OS: Windows 7 x64 with SP1
Going up against the FX-8150 is a 4-core/8-thread Intel i7-2600K running on a ASUS Maximus IV Extreme with other identical control components. Instead of using the 4 core/4-thread i5-2500K, we decided that it would only make sense to pair a 8-threaded processor against a 8-threaded processor. Using the AMD Radeon 6990 also ensures that any graphical bottlenecks would be taken care of.
Overclocking/Temperatures & Diatribe:
The only logical reason why anybody would buy a top of the range unlocked multiplier processor would be to overclock it – so we did.
Despite our best efforts, we could only push our FX-8150 sample to 4.7GHz on Air (CPU-Z Validation Link). This was done by applying the "Extreme OC" preset on the motherboard for overclocking timings and secondary voltages, applying a 23.5x multiplier and manually setting the CPU voltage to 1.47v. At this voltage, temperatures were around 70 degrees celcius on full load (Prime95 Large FFTs). Your actual mileage may vary, but according to AMD engineers the typical Air Cooling setup will achieve ~4.6GHz with all cores/modules enabled. The good news is that there is no "cold bug" at sub-zero temperatures, and LN2/phase change overclockers have been running this at higher frequencies.
The Intel i7-2600K setup was also set to 4.7GHz (lowered from 5.2GHz) and 1.47v for "clock for clock" comparison sake.
|Since we're not chasing world records, we tested our overclocks over many hours of Prime95 Blend and Linpack to stress the CPU/Memory subsystem. Some other hardware sites and ignorant end-users seem to always show improbable overclocks which have no other utilitarian use other than to boot into windows and take a CPU-Z screenshot or maybe run a few (borderline stable) benchmarks. Worse still is the practice of "disabling cores" to achieve higher clocks, which is just blatent misrepresentation and counter-productive.|
In the UEFI bios, we also set:
- CPU-NB Frequency set to 2400MHz from 2200MHz and left the HT Link Speed at Auto (2600MHz). We played around with the voltages but failed to go any higher.
- Used the 1600MHz memory strap. We will cover memory frequency/latency scaling in a later article.
- Disabled APM (application power management, induces clock throttling when TDP limits are hit)
- Enabled HPC (High Performance Computing, not sure what it does exactly but we see marginally higher scores across the board with it turned on)
- CPU/Chipset/Memory power regulation settings set to their most aggressive
Cool & Quiet, C1 state, C6 state and other power saving options were turned off during overclocking - we really can't fathom why anybody will choose to turn them on as they have been proven to induce:
- framerate jitter in games
- latency problems for audio/video applications
- reduced storage performance
- stability problems when overclocking/resuming from standby
Moreover, the power savings from turning these features on is almost negligible, especially on a 125W TDP CPU (and presumably paired with a power hungry GPU as well).
Ecomentalists who pay a premium for "Green" edition mechanical harddrives are also suckers, as they save an insignificant amount of power but have to live with crippled performance and annoying spin-up/spin-down head wear.