Overclock G5?

Posted:
in Current Mac Hardware edited January 2014
Has anyone done this yet? You could probably over clock each G5 to 2.25GHz.
«1

Comments

  • Reply 1 of 24
    Quote:

    Originally posted by Altivec_2.0

    Has anyone done this yet? You could probably over clock each G5 to 2.25GHz.



    Well, there's a (little) problem. In order to overclock the G5, you have to overclok the bus and the system contoler too. Or you can use the (few) FSB ratios that the G5 supports (i think they are 1:2, 1:3, 1:4, 1:6, ...), meaning that, in order to use the next multiplier with the same 1GHz bus, you'd have to get a 2GHz G5 to 3 GHz. That's not possible, unless you have some liquid nitrogen at home.
  • Reply 2 of 24
    placeboplacebo Posts: 5,767member
    The G5's cooling system is calibrated with great precision. Each model of the G5 has a different calibration, and you'd have to know how to safely hack the cooling system if you are going to overclock it.



    And, as Mac Force noted, the buses are very picky.
  • Reply 3 of 24
    Quote:

    Originally posted by Placebo

    The G5's cooling system is calibrated with great precision. Each model of the G5 has a different calibration, and you'd have to know how to safely hack the cooling system if you are going to overclock it.





    Or you could just have all the fans run at full speed whenever the CPU is being overclocked.



    [Edit] And there should be some source code to control the fans in Darwin, otherwise it would be unsafe to run Darwin on a G5.
  • Reply 4 of 24
    stoostoo Posts: 1,490member
    I thought that the G5 fans ran at full speed unless told otherwise. (For example, don't PowerPC Linuxes' users have to put up with full fan speed, as they aren't under OS control yet?) If an OS is required, the possibility of the machine being destroyed by booting without a valid OS would look a bit stupid.
  • Reply 5 of 24
    tidristidris Posts: 214member
    Quote:

    Originally posted by Stoo

    I thought that the G5 fans ran at full speed unless told otherwise. (For example, don't PowerPC Linuxes' users have to put up with full fan speed, as they aren't under OS control yet?) If an OS is required, the possibility of the machine being destroyed by booting without a valid OS would look a bit stupid.



    That makes sense. So maybe the real issue is to tell the fans not to slow down when running OSX on an overclocked G5. Maybe the Darwin source code would give a clue as to how that can be accomplished.
  • Reply 6 of 24
    bartobarto Posts: 2,246member
    Quote:

    Originally posted by Stoo

    I thought that the G5 fans ran at full speed unless told otherwise. (For example, don't PowerPC Linuxes' users have to put up with full fan speed, as they aren't under OS control yet?) If an OS is required, the possibility of the machine being destroyed by booting without a valid OS would look a bit stupid.



    That is true, although most Mac Linuxes include or will include drivers to control the fans.



    Barto
  • Reply 7 of 24
    ....Why?





    Phrase your answer carefully, or you'll hurt my G4's feelings.
  • Reply 8 of 24
    ryaxnbryaxnb Posts: 583member
    Can you overclock a bus?
  • Reply 9 of 24
    Quote:

    Originally posted by Tidris

    Or you could just have all the fans run at full speed whenever the CPU is being overclocked.





    Nice idea, you wouldn't be able to hear yourself think! The G5 is a wonderful machine in that it is quieter with 9 fans than a G4 is with only two. However, you get all 9 of those suckers goin (startup in FW target disk mode if you want to hear your 747...I mean G5 rev up.) and your gonna have one heck of a loud computer. Not acceptable for most, I know I wouldn't deal with it. Wait for the Rev. B or C and you'll see a 3.0ghz without overclocking.
  • Reply 10 of 24
    >Wait for the Rev. B or C and you'll see a 3.0ghz without overclocking.



    What's the point? You could overclock a 3GHz G5 to 3.5 or higher.
  • Reply 11 of 24
    amorphamorph Posts: 7,112member
    Quote:

    Originally posted by ryaxnb

    Can you overclock a bus?



    Sure.



    You can technically overclock anything that runs by a clock. You just make the clock tick faster, until you reach a point where the bus or CPU or whatever device can't keep up.



    You can think of it as a bandleader calling a song at the fastest tempo his band can play.
  • Reply 12 of 24
    Damn, I was hoping to get my 1.6 up to 2.0!
  • Reply 13 of 24
    Quote:

    Originally posted by Amorph

    Sure.



    You can technically overclock anything that runs by a clock. You just make the clock tick faster, until you reach a point where the bus or CPU or whatever device can't keep up.



    You can think of it as a bandleader calling a song at the fastest tempo his band can play.




    Yes, but the 1 GHz buses in the 2 GHz G5 already must have trouble keeping up, materialy, with their frequency. Overclocking them is pure dream, especially that we don't know where it is controlled?
  • Reply 14 of 24
    amorphamorph Posts: 7,112member
    Quote:

    Originally posted by Mac Force

    Yes, but the 1 GHz buses in the 2 GHz G5 already must have trouble keeping up, materialy, with their frequency. Overclocking them is pure dream, especially that we don't know where it is controlled?



    I'm sure that's true. But the question was whether you can overclock a bus, and technically, you can. The busses in the 1.6GHz and 1.8GHz models should be clockable to at least 1GHz, in theory...
  • Reply 15 of 24
    tidristidris Posts: 214member
    Quote:

    Originally posted by Tidris

    That makes sense. So maybe the real issue is to tell the fans not to slow down when running OSX on an overclocked G5. Maybe the Darwin source code would give a clue as to how that can be accomplished.



    The code to control the G5 fans appears to be in file PowerMac7_2_CPUFanCtrlLoop.cpp of the Darwin AppleMacRISC4PE-102.2.1 module, in case anybody cares.
  • Reply 16 of 24
    outsideroutsider Posts: 6,008member
    Quote:

    Originally posted by Amorph

    I'm sure that's true. But the question was whether you can overclock a bus, and technically, you can. The busses in the 1.6GHz and 1.8GHz models should be clockable to at least 1GHz, in theory...



    The 1.6 maybe even higher than 1GHz. Less memory traces due to the lack of 4 DIMM slots. I wonder, though, if the PCI bus will scale up as well. 200MHz is a 25% increase in clock speed from 800. That would make for a 41.6MHz PCI bus, or 83.3MHz slots. So there must be more to overclocking that just bumping up the clock itself. You have to find the bus to PCI ratio circuitry, probably in the form of resistors, and modify those too.
  • Reply 17 of 24
    grecygrecy Posts: 15member
    this post over at www.arstechnica.com touches on the question at hand:



    Quote:

    Does anybody here have any hints on how to set the CPU/bus speeds on the G5.



    We tried clocking a DP 1.8GHz to DP 2GHz by copying the settings on the CPU card of a DP 2 GHz but with no luck. It still boots at 1.8GHz.

    The 2 GHz modules will boot at 2 GHz in the 1.8 case but the fans run at full speed so it must need to have them recalibrated for the faster CPUs (I believe there is Apple software to do this). Even with the 1.8 modules modded to what we believe are the 2GHz settings they still boot at 1.8, even in the 2 GHz case so we must be missing something.



    Any tips/links etc will be most appreciated, and of course this was all done in the interests of science and not because we are hopeless meddlers with beautiful gear that runs perfectly acceptably at its rated speed.



    Is it possible there is software control for G5 CPU/bus speed like some of the G3s? In that case the resistors we were changing were

    probably voltage related.



    No luck as yet, but I'm keeping my eyes on it.

    With M.Isobe on the case, I don't think it will take too long.



    -Dan
  • Reply 18 of 24
    No one has been successful?



    I also thought that the fans were controlled automatically (whether with software or hardware code) with the variable of heat dissipation.



    It seems idiotic to run extra code on the processor when it could be controlled another way...but i guess the current way is 'cheaper.' But that usually carries a price even, as the O.S. has to worry about the fans...or the firmware...or what ever.



    -walloo.
  • Reply 19 of 24
    0010001100100011 Posts: 21member
    Sorry to bring an old topic back from the dead, but in the last two years, has anyone found a way to overclock a G5?



    I've regretted purchasing my rev. A single 1.8GHz PowerMac G5 since the day I bought it. It was $3000, and then supposedly the rev. Bs worked a hell of a lot better, then the price went down half to $1500, then the iMac got a 2.0GHz processor making it faster than may PowerMac, and finally, Apple decided to stop making single 1.8GHz PowerMac.



    I'd be incredibly happy if I could just upgrade the CPU to something beyond 2.0GHz, but it seems as though the G5 PowerMacs were intentionally built to make sure that you'd have to buy a new PowerMac if you wanted upgrade the CPU; that's bullshit. Before I got my G5, I was running a 266MHz G3. That machine was great because it allowed me to upgrade the ZIF CPU, which I later did - 466MHz; I was thinking about upgrading it again to a 1GHz G4 ZIF (Sonnet) before I got my G5, but I obviously got the G5 instead.



    I really feel like Apple screwed me with my current G5, so I'll ask the question again:



    Seeing as how the G5 CPU cannot be upgraded, has anyone found out a way to overclock it, and if so, how?
  • Reply 20 of 24
    xoolxool Posts: 2,460member
    Only thing I've done to my G5 is overclock my ATI card using ATIccelerator. I use CHUD to disable the annoying chirping sounds too.



    Comparing the rev b/c G5 at my office to my rev a G5 at home (both Dual 2 GHz) I can tell a few differences. The newer machine is certainly quieter and they resolved the chirping issue. This may be subjective however, as my office environment has a lot more ambient noise than I have at home.



    Now that I mention it... I have AppleCare. You think I could get them to replace my power supply or whatnot to get the unit's noise down?
Sign In or Register to comment.