Overclocking the Core Duo

Discussion in 'Windows, Linux & Others on the Mac' started by Vlade, Apr 12, 2006.

  1. Vlade macrumors 6502a


    Feb 2, 2003
    Meadville, PA
    Has anyone read anything or experimented with overclocking the core duo? I don't know how apple decided to handle the clocks on the core duos (either EFI or hardware) but I'm always curious about that kind of stuff because I love to overclock everything I can :). I know the chip can half its multiplier if there is little load on the CPU, I'm guessing thats software controlled or driver controlled somewhere.

    PS: Please don't talk about whether or not we should overclock, yes we all know the dangers of overclocking but some of us like to do it anyway :)
  2. Benjamindaines macrumors 68030


    Mar 24, 2005
    A religiously oppressed state
    I don't know how you would to it but I DO know that if you have an iMac or a Mini the cooling is more then enough to over clock... I wouldn't recommend it in the MBP (you will melt you leg hairs)
  3. Demon Hunter macrumors 68020

    Mar 30, 2004
    Haha, overclocking rocks. It would be exciting if it was in the EFI. The Core Duo isn't a Celeron, though, so I don't know what kind of increase you'd get.
  4. excalibur313 macrumors 6502a


    Jun 7, 2003
    Cambridge, MA
    I've been wondering this too. Can you do it in an operating system (like overclocking a video card) or is it changed upon boot up?
  5. rayray1017 macrumors newbie

    Apr 1, 2006
    Texas, Houston
  6. Airforce macrumors 6502a


    Jan 12, 2006
    The 2.16ghz core duo has been able to hit 3.4ghz. It's a great overclocker, but I wouldn't be overclocking those chips in such small spaces....bad idea for any cpu.
  7. dmw007 macrumors G4


    May 26, 2005
    Working for MI-6
    You are right, I have seen some benchmarks of over-clocked Core Duos (up to 3.4GHz) and the performance is incredible. Not so sure how good of an idea it would be to OC a Core Duo in a MBP, maybe in a iMac though. :)
  8. zap2 macrumors 604


    Mar 8, 2005
    Washington D.C
    I would think the iMac could handle a very hot chip, as i'm sure the G5 was a lot hotter.

    But that also assumes Apple used the same fan as the G5 iMacs
  9. dmw007 macrumors G4


    May 26, 2005
    Working for MI-6
    Good point, the G5 does run hotter than a Core Duo. :)
  10. tonyl macrumors 6502

    Jan 18, 2006
    CPU-Z can be used in windows for overclocking, but no working version for i945GP (iMac logic board). Since you can change the Vcore, so the OCing will be very limited.
  11. aplasticspork macrumors regular

    May 27, 2004
    Seattle Wa.
    The macbook pro might be able to handle a bit of an overclock (not much though). Someone on this forum said that they got the X1600 in their macbook pro up to 470 core, 470 memory. Mine is at 313 core, 297 memory by default, and it can go up to 473/526, though at those speeds there are video issues. It is stable, however at 450/450 (and Oblivion gets decent framerates at almost the highest settings). I'm not sure how much of a temperature increase that is (as there aren't any temperature monitors for the intel macs yet), but it's probably significant. I think that just a cpu overclock might actually be possible, but I personally wouldn't be willing to be the lab rat since there aren't as obvious signs when your cpu is too hot. with the gpu there are graphics issues when you go too high, so you know to lower it.

  12. 5683565 Suspended

    Feb 18, 2006
    Hong Kong
    I generally run my Graphics Card at 510/560 without any problems. I am surprised that people have issues at lower frequencies.
  13. aplasticspork macrumors regular

    May 27, 2004
    Seattle Wa.
    This is in the macbook pro, not the imac. The imac has much more space for airflow and cooling than the macbook does. As such, I would expect the graphics card in the imac to go quite a bit higher.

  14. isgoed macrumors 6502

    Jun 5, 2003
    Where is the Clock Crystal?

    I used an application CPUFSB on windows to overclock my athlon PC. It works by changing BIOS settings while in Windows. I tried to do it on my Mac Mini but without results. I wonder if it is possible at all since the mini only emulates a BIOS and it might even emulate a BIOS that has no "System Management Bus connection".

    Changing the FSB works by changing the frequency of the clock crystal. You need to know which crystal is in your system. A clock crystal looks like this:


    I looked at pictures from disassembled mini's (1) (2) (look at download for high res), but could not find one.

    So I opened up my mini and indeed found a crystal. I don't have a digital camera, but I attached a schematic of what is underneath the airport card. The chips read:

    Crystal: 24. 576H6B
    agere L-FW323-06 1394A LINK/PHY 0607S 50284247
    B: SST 25vfo 16B 50-4C-S2AF
    32 768 KDS0604
    +330 e62
    +J8 EP
    F: KL1 T2
    G KL1 T2

    the Agere chip seems to be firewire (1394). And also the crystal is attached to the agere chip, so I don't think It's the frequency chip. Under the ram slots there is pretty much nothing. I have not lifted my mainboard completely out, but by looking at the pictures I concluded that there was no clock crystal on the mac mini.

    I am now confused how the BUS-speed is controlled on the new intel chips. It might be that they are using onchip crystals. On the internet i found two documents about the PLL bus controller of the 945 chipset (1# PDF 2.1 MB) (2# PDF 2.3 MB).

    Traditionally you could also solder jumpers on a mainboard to change the CPU-frequency. I don't know if it's possible on the new chipsets. The recent overclocks of core duo's and core celeron's (on PC's) were done by increasing the FSB in bios.

    arstechnica have looked at the chipset of the iMac and found:
    Finally: has anyone looked in changing FSB settings from within EFI (extensible firmware interface)?

    Attached Files:

  15. biohazard6969 macrumors 6502a


    Feb 23, 2005
    toronto canada
    wow thats a lot of info, i really hope someone finds a way to do this, i'm an overclocking addict myself, and would love to try this on my imac
  16. balamw Moderator


    Staff Member

    Aug 16, 2005
    New England
    Silly me, I often find that overclocking is one of the two main sources of instability in many of the Windows boxes people ask me for help with. Cheap and/or incompatible RAM is the other.

  17. auhlixer macrumors regular

    Apr 15, 2006
    Philadelphia, PA
  18. ChrisFromCanada macrumors 65816


    May 3, 2004
    Hamilton, Ontario (CANADA)

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