G5 Overclocking

How to?..should I?..Has anyone done this yet? Any help or suggestions would be appreciated.

dogboy443

I don't believe it is possible... And I certainly would not try it with all the heat issues they have. I believe that the G5 is fast enough.

I suggest you stick with using it for what it is meant for, over cooking it wouldn't help the taste. ...

its possible but it requires sodering stuff on the motherboard, and all in all will probably break your comp. these computers run hot enough as it is, they definately dont need overclocking.

menace3054 said:

its possible but it requires sodering stuff on the motherboard, and all in all will probably break your comp. these computers run hot enough as it is, they definately dont need overclocking.

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That is for the G4, but the G5 can't be overclocked.
The G4 had it's clockspeed that was a multiple of it's FSB, and by changing some resistances on the CPU board (soldering) you could change that multiplier.

The G5 works very differently, faster G5 CPUs have a faster FSB, while the multiplier remains the same (2x or 3x, depending of the model).

So changing the multiplier on a G5 (if it is even possible, which I doubt) would immediately fry the CPU, as it's clockspeed would rise way too much.

Little example:
PowerMac G4 running at 500MHz: FSB 100Mhz 5x
changing multiplier to 6x will make the G4 run at 600MHz

PowerMac G5 Running at 2GHz: FSB 1GHz 2x
changing that multiplier even just a half step to 2.5x means 2.5GHz...no CPU will survive such a raise without some serious cooling mods (no, simply liquid cooling it won't be enough).

i got any idea for a project if someone will fund me,

powermac G5 under phase change :doctor:

i have been reading up on vapour phase change cooling that is why i have not been as active here.


i have my eMac under a water setup


the_new_guy

You have confused me.

validpretense said:

You have confused me.

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Don't feel alone

You would have to find a way to increase the FSB if you wanted to overclock the G5. As has already been mentioned, changing the multiplier would create a clock speed that was far too high. They system would not boot at that speed, but I doubt you'll do any damage. To carry the overclock even further you'll have to find a volt mod.

Yeah, I want to turn my G5 into a stove!

sevenhelmet said:

Yeah, I want to turn my G5 into a stove!

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Unplug the fans. :dummy:

Amen-Moses

the_New_Guy - I have already started the process of designing a triple cascade phase change for my G5, Prometeia or Vapochill jut wouldn't be enough, ha. This system should bring temperatures down to about -100C on the core, cold enough??? In my other project I have already made 98% pure copper water blocks for the stock cooling to relplace those ugly aluminium alloy blocks, that should, in theory, bring my temperatures down about 5-10C. Yes G5's run hot, but after overclocking an old AMD XP 2500+ to 3.0GHz on air cooling, you've never seen high heat, lol. Theres always some kind of cooling that will compensate for the high heat produced by overclocking.

I will post all my work on my website soon once I get some time to upload pictures and plans for my cases and G5 projects.

A warning to everyone phase change systems, even Prometeia's and Vapochill systems, require a lots of labor extensive modifications to your system and should not be attempted unless you have knowledge of HVAC systems, condensation principles, and great knowledge of your computer. I am very lucky having an HVAC engineer as one of my best friends who just graduated from college. Not to mention my dad's machine shop where I can CnC all my own custom blocks.

How about an alternate approach... despite Googling for it, I cannot find such a thing, but Freescale must have a roadmap for the PowerPC chips. What comes next after the G5 chips (PPC970, I believe?)? Is there going to be a "G6", or a faster G5?

I wonder if someone could design a daughter board which was plug compatible with the G5 pin grid, that could bring a faster processor to current PowerMac G5 owners? To do this, the daughter card would need a faster processor and a lot of on board cache, since the front side bus speed can't be changed.

Has anyone heard of such an effort? I bet there would be quite an audience for such a thing... if Freescale is enhancing the PPC chips in the first place!

To tell you the truth, I don't think Freescale took PowerPC processors any farther than later G4-era speed. The last chips from Freescale/Motorola that Apple used were in their G4 Powerbooks since the G5 couldn't go mobile because of obvious heat issues. After that, Freescale has been concentrating more on using PowerPC in embedded systems and communications devices rather than computers. IBM had a lot more to do with with designing the PowerPC G5 than anyone else. When it comes to next generation PowerPC architecture, I think IBM is the lone ranger in development. I think the G5 was their Power6 processor, and Power7 is supposed to be some fantastical 10GHz processor or something. I'm not even sure if IBM is still developing Power7 because they really put a lot of their effort into their Cell processor.

Overclocking a G5? It's probably possible, but it may take someone who knows what they're doing a while to figure out what controls the multiplier/frontside bus and voltage. You can up the multiplier and overclock a CPU, in which it won't do any damage at all (it just won't work), but unless you raise the voltage you won't be getting anywhere. It could also be possible that the G5 uses an internal clock generator of some sort. If this is on-die the CPU, there's no way you will be able to overclock unless someone can figure out how to program it. If it is on the motherboard or processor board, someone could figure out how to make a different one and solder it in place of the original one.

That's a lot of effort for probably little gain. Unless you can use phase change cooling on the G5, even with water cooling you will never be able to hit 2.8-3.0GHz even with a 2.7- or 2.5GHz model. Things have changed a lot in the overclocking world, and boy do I miss the old days where you would just change around some dipsticks and cross your fingers while pressing the power button...

Yeah I miss the days of overclocking processors with dipsticks... I just finished putting the new water blocks I CnC'd out of copper today on my extra set of processors. If nothing else they look cool. I'll have pictures up on my site later this week. I hope to put them in tonight and see if it makes any difference in the temperatures. I believe it will since the stock Apple blocks were made from aluminium and had poor flow pattern inside the block. I'll let you know how everything works.

As for overclocking the G5, I have no doubt someone will figure it out. People have always said that processors are "not overclockable" like the old Willamette core P4. However in a few months some clever fellow figured out a firmware and BIOS hack which allowed you to overclock them. In fact my parents Dell has been overclocked with a Willamette core P4. Just give people some time and I'm sure they'll figure something out. I am fairly new to Macs but have been on 3DMark teams for the past 4 years, since I was 15, for overclocking PCs and building extreme cooling rigs, therefore I'm not fully up to speed on what IBM has been developing for Macs, and now that Macs are using Intel processors, I'm sure we'll be seeing some Mac Pro overclocks soon... I'm not brave enough to try anything on mine yet.