Eeeerrrmmmm... All you b33ches with the l33t 4870, flash this BIOS and enjoy higher clocks and supposedly better fan profile as well 
ReMOSitory :: mvk.tech :: NVIDIA GeForce GTX 280 GTX 260 9800 GX2 9600 GT 8800 GTX ATI Radeon HD 4870 HD 4850 HD 3870 X2 HD 3850 2900 XTX - MVKTech
Source: 4870 ASUS TOP BIOS (upto 900MHz in CCC) - XtremeSystems Forums
Tools Needed
1. USB Flash drive
2. Win98 Boot Files (Mr. Supra to give the link
)
3. The BIOS files (Of course
)
4. ATiFlash 3.60
Steps:
1. Save the atiflash.exe and .cfg file on the USB drive.
2. Use GPU-Z 0.2.6 (TechPowerUp GPU-Z v0.2.6) to take a dump of the stock BIOS and save it. Take a dump of this on the USB stick as well.
3. Rename the downloaded ASUS BIOS to mod.rom (.rom / bin as the case maybe - The ASUS file is a rom file) and save it on the USB drive.
4. Restart PC and it should boot in Win 98 DOS mode (Check for Boot Drive priorities if it doesn't).
5. The command for flashing is atiflash -p 0 *.rom / bin.
Once its done, restart the PC and you should be good to go

ReMOSitory :: mvk.tech :: NVIDIA GeForce GTX 280 GTX 260 9800 GX2 9600 GT 8800 GTX ATI Radeon HD 4870 HD 4850 HD 3870 X2 HD 3850 2900 XTX - MVKTech
Disclaimer:
Flash at your own risk. I'm not responsible if you brick your cardhyeah:
Source: 4870 ASUS TOP BIOS (upto 900MHz in CCC) - XtremeSystems Forums
Tools Needed

1. USB Flash drive
2. Win98 Boot Files (Mr. Supra to give the link

3. The BIOS files (Of course

4. ATiFlash 3.60
Steps:
1. Save the atiflash.exe and .cfg file on the USB drive.
2. Use GPU-Z 0.2.6 (TechPowerUp GPU-Z v0.2.6) to take a dump of the stock BIOS and save it. Take a dump of this on the USB stick as well.
3. Rename the downloaded ASUS BIOS to mod.rom (.rom / bin as the case maybe - The ASUS file is a rom file) and save it on the USB drive.
4. Restart PC and it should boot in Win 98 DOS mode (Check for Boot Drive priorities if it doesn't).
5. The command for flashing is atiflash -p 0 *.rom / bin.
Once its done, restart the PC and you should be good to go
