Overclocking iMac 27's ATI 4850 & Sound Issues

Discussion in 'iMac' started by brianjcho, Aug 3, 2010.

  1. brianjcho macrumors newbie

    Jul 30, 2010
    Hello I am a new iMac 27' owner (i7 refurb) and wanted to get the most out of this machine in win 7.

    How safe is it to OC' the 4850 and to what degree can I expect to push the clock speed? Which program would you recommend?

    The audio from the default speaker sounds so much better in OS-X. I tried installing the realtek drivers and honestly it didn't help much. Is there any work around this or am I doomed to purchase a decent stereo system now for win7 gaming :p
  2. TMRaven macrumors 68020


    Nov 5, 2009
    As far as overclocking the mobility 4850 goes, use msi afterburner. In order to get msi afterburner to overclock mobility cards, you need to edit "allow unofficial overclocking" line in msi afterburner's config.txt file. Just open it up in notepad and find the "allow unofficial overclocking' line, and change the 0 to a 1, then save the file with its original name.

    You can push the mobility 4850 to pretty high speeds, because the 27 inch iMac has rather good cooling when you crank the fan speeds up. If you crank the odd fan up to max, you can get away with desktop 4850's clock speeds (625mhz core and 990mhz vram) An overclocked mobility 4850 with those clocks will perform exactly like a desktop 4850.

    With the odd fan maxed, you won't see your gpu's temp rise above 70c. To set the odd fan to max rpm, rev it up with smc fan control on osx, then restart the computer (not shut down) and go into windows.

    I don't know what to say about the sound quality. Even after calibration of the window sound options, I still find the sound to be inferior to osx as well.
  3. brianjcho thread starter macrumors newbie

    Jul 30, 2010
    thanks tmraven, your other reply on the sc ii optimization thread has been extremely helpful as well.

    you are the man!

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