Overclocking iMac

Discussion in 'iMac' started by Yateball, Nov 8, 2007.

  1. Yateball macrumors regular


    Jul 25, 2007
    Hey everyone,

    I am interested in some kind of tutorial for overclocking my imac. I know how to do this on a PC but have never tried it with a mac.

    I googled my butt off and wasnt able to find anything that was actually helpful.

    If anyone can help or knows where a tutorial is, please let me know.

  2. SuperCompu2 macrumors 6502a


    Jul 23, 2006
    I believe BIOS is needed in order to overclock, and iMacs lack BIOS.

    There may be some other way, but I am not familiar and probably wouldn't attempt it with the poor cooling in such a cramped space.
  3. jf8 macrumors regular

    Aug 8, 2007
    first: Overclocking is generally a waste of time, unless you're making drastic changes. And with a 800mhz stock FSB and a 800MHz max in-spec FSB... you won't be able to do a whole lot.

    A BIOS is not required. It just so happens that many retail motherboards support overclocking in the BIOS. Many also support overclocking in software, and this is done either by system (manufacturer)-specific software, or by generic software that works with specific clock chips (see ClockGen for Windows.)

    If ClockGen supports the chip on the iMac, you could attempt to overclock.. in Windows. But there are obviously risks with RAM & PCI Express bus speed.

    The iMac (new) has a PM965 chipset, which is a mobile chip. In the past, I've overclocked an Intel 915GM (Pentium M) mobile chipset, using both built-in BIOS facilities and ClockGen.

    If the iMac used LGA775, you could use a pin mod to increase FSB to 1066MHz or 1333MHz. But Socket P / the PM965 only support 800MHz, which is what the new iMacs use.

    I wouldn't be so concerned about the cooling...I would imagine that all of the current iMacs are designed so that they could potentially work with a 45w TDP chip (instead of 35w.) Intel's roadmap shows 45w quad-core mobile CPUs in the second half of 2008.
    Right now the only Intel mobile CPU with a 45w TDP is the 2.8GHz X7900.

    At any rate, I think you'd need to adjust the voltage to cause a significant change in power draw.
  4. combatcolin macrumors 68020


    Oct 24, 2004
    Northants, UK

    Overclocking Macs is generally a lot harder than doing the same with a self build PC.
  5. Yateball thread starter macrumors regular


    Jul 25, 2007

    Thanks a lot for your help... you're probably right though, sounds like it would me more trouble than it's worth.

    At least I know it can be done lol.

    When the first post said you HAVE TO have BIOS I didn't think that was right, but at any rate, thanks again.
  6. kingofcomputing macrumors newbie

    Oct 17, 2009
    Wondered This

    I always wondered this, but i have no clue how. I guess that dual booting with windows would be the best way. I want to overclock my imac because i have a lot of cooling overhead with SMC Fan Control. Hoping to make the 2.16 reach my Macbook Pro's 2.33 clock speed to get that extra edge.
  7. Hellhammer Moderator


    Staff Member

    Dec 10, 2008

    iMac uses SPECIAL CPUs from Intel (E8xxx) and those are 44W respectively outclassing 3.06GHz used in 2008 iMac (55W) and 2.66GHz and 2.93GHz used in 2009 iMacs (35W)

    IMO OCing isn't worth it unless it's over 500MHz
  8. nullx86 macrumors 6502a


    Jun 26, 2009
    Wilmington/Jacksonville, NC
    Holy thread revival batman! There is a tool to overclock in OSX, but on an iMac, its not worth it, because you'll wind up killing it. On a Mac Pro, sure I can see the benefit of overclocking to gain an extra GHz out of those Xeons, but not on an iMac which as Hellhammer has said, use special laptop style CPUs (my iMac has a E8XXX for example) which overclocking would be practically useless.
  9. MacHamster68 macrumors 68040


    Sep 17, 2009
    whats the point of overclocking anyway
    ok you gain some speed , if done sensible the system stays stable with luck ,but sensible only means some Mhz more , and for these couple Mhz you have no warranty any more, lost your apple care ,
    for overclocking to the max you also need cooling which is very limited in the iMac to start with ,unless you want to give it a hunchback ,best with oil pipelines hanging out of it for cooling :eek:
    its a iMac not a oil rig:eek:
  10. charlesbronsen macrumors 6502a


    Oct 22, 2008
    Toronto, Ont
    I could see benefits from clocking video card in bootcamp if you play video games but as for the cpu/ram I think its a lost cause.

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