ATI will introduce Overdrive 4 with the next Catalyst Driver scheduled in March.
Previously you could only overclock your GPU core with Overdrive, and only by a rather small amount.
Now you can overclock both core and memory and the frequency range will be increased to 75% of the next higher class product.
For example the X800 Non-Pro (400 Mhz / 350 Mhz) could be overclocked up to 456 Mhz Core (400 + (475-400) * 0.75). The memory overclock would be 425 Mhz (350 + (450-350) * 0.75).
This rule does not apply to the XT and XT PE versions of the card and it does not apply across video card generations.
One requirement for Overdrive 4 is that a digitally-signed "SecureBios" is present on the video card. At the moment it is unclear whether current video cards without the signed bios will work. But we think ATI wants to let as many users as possible use the new Overdrive so exceptions will probably be made.
Another requirement is that a thermal sensor circuit MUST be present on all cards supporting Overdrive 4 because temperature monitoring will be used to prevent overheating damage to the chip.
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Source:
TechPowerUp
ATI's Overdrive 4 plans
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