Clock Rates And Lethal Boost Mode
Overclocking with the Push of a Button
Engaging Lethal Boost mode is pretty simple: push the Lethal Boost button while the computer is running and then re-boot. The Toxic HD 7970 GHz Edition loads its settings from a second firmware containing higher clock frequencies and a more aggressive fan profile.
First, we have the original factory settings:
Then we push the Lethal Boost button. In the picture below, the button is to the left of the CrossFire connectors.
Lethal Boost Mode now gives us higher clock rates and a new PowerTune limit that extends to 50 percent (from 20).
When the Radeon HD 7970 GHz Edition launched, we discovered that if the card gets overclocked (or underclocked) by only 1 MHz, it holds that frequency, behaving like an ordinary Radeon HD 7970. It doesn’t throttle down, though, even when it's idle. The card sucks down 50 W or so, and ZeroCore Power stops working. We use the fixed clock rate to compare Sapphire's Toxic HD 7970 GHz Edition 6 GB to older cards.
Our Benchmark System
|Benchmark System (Open Case)|
|CPU||Core i5-2500K (Sandy Bridge), Overclocked to 4.5 GHz|
|Cooler||Prolimetech Super Mega + Noiseblocker Multiframe|
|Memory||4 x 4 GB Kingston HyperX DDR3-1600|
|Motherboard||Gigabyte Z68X UD7-B3, Z68 Express|
|Operating System and Driver||Windows 7 Ultimate x64 Catalyst 12.6 WHQL|
|Case||Lian Li PC-T60A ATX Test Bench|
First Benchmarks At Stock Settings
We started by taking a quick look at how the Sapphire Toxic HD 7970 GHz Edition 6 GB fares at its stock settings. This gives us a reference point for our more in-depth benchmarks.
Our second test, Metro 2033, was also run at 1201 MHz, fixing its clock rate in place.
At a resolution of 2560x1440 pixels, Sapphire's Toxic HD 7970 GHz Edition 6 GB and Gigabyte's Radeon HD 7970 Super Overclock with 3 GB perform about the same. The Gigabyte card does manage to deliver better power consumption results compared to Sapphire's board at this fixed clock rate, interestingly enough.