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You are here: MacNN Forums > Hardware - Troubleshooting and Discussion > Mac Desktops > I've Overclocked my G5

I've Overclocked my G5
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Fresh-Faced Recruit
Join Date: Oct 2006
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Oct 18, 2006, 11:38 AM
I have been able to "soft over-clock" my G5 via a HACK.

It does not seem stable, and sometimes it works, but after a reboot it won't.

I'm getting higher scores in OpenGL apps and Render times are faster in QTPro for DV to h.264 encoding.

I'll be posting some results here soon, just want to get the word out for others to try.

BE WARNED, I don't lay any claim that this hack won't KILL YOUR G5.
Posting Junkie
Join Date: Jan 2006
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Oct 18, 2006, 01:41 PM
What is the new speed?
Mac Enthusiast
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Oct 18, 2006, 09:29 PM
Originally Posted by imitchellg5 View Post
What is the new speed?
It was 2.1GHz (from 1.8GHz).
12" Powerbook 1.5GHz/SuperDrive, 1.25GB Ram, 80GB HD, Airport Extreme, Mac OS X 10.4.11 Tiger
iBook (Late 2001)600MHz/Combo, 640MB RAM, 20GB HD, Airport, Mac OS X 10.3.9 Panther — web server
Professional Poster
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Oct 18, 2006, 10:24 PM
Interesting, but iffy.
The era of anthropomorphizing hardware is over.
Posting Junkie
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Oct 18, 2006, 10:55 PM
Isn't the original strange k9 post about support for OpenGL 2.0 features only?

ie. Not overclocking but updating video drivers?


Oh, I see he claims his 1.8 was reported as a 2.1 after the hack... until this:
Update, after some benchmarking too confirm this I let my mac sleep again, on a hunch I checked the processor performance again, once more it was set back to "reduced".

I then set it back to "highest", a bad move on my part as my mac locked-up, I waited a bit to see if it would recover, however it did not.

Upon a forced restart, my mac would no longer boot, the power came on and drives spun up, but no video or boot chime. After a few hours of checking on the web and SMU resets, I found that if I held the power button for a long time, the OpenFirmWare programers interface would come up, I reset the nvram and rebooted. My mac was back.

The bad news is: I have not been able to duplicate my earlier results, doing everything I think I did before.
Fresh-Faced Recruit
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Oct 19, 2006, 08:19 AM
Yes, that update to the page was there before I installed the Hack.

My mac is linked, it Dual 2.0, not SP 1.8, but I don't know how fast it's running via this Hack.

ASP reports 0mHz, after the sleep deal, but when I encode a 30min DV file to h.264 my times are faster by about 3 minutes vs before "sleep". Time with a stop watch so some deviation here.

I'm not really a "bench marker" most of the work I do is encoding video, so it's faster for me, but I can't really "use" it as all the bugs in the "OS" part of the hack make my workflow fail.

I'll download Cinebench and post back a before and after, when I get a chance.

After that I'm rm -f / this hack as it's taking up space on one of my drives, that I need for work.

It's a nice small speed boost, but all the bugs make it unusable.
Mac Elite
Join Date: Mar 2006
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Oct 19, 2006, 03:36 PM
Be careful with this. You could end up with bad renderings if things are not cooled well enough. That would sort of negate any gain you got. I mean, if you are 10% faster, but you lose 10% of your renderings and have an unstable system, you don't gain anything.

But if you get it working correctly, it would still be awesome. Some serious aftermarket cooling would be nice.
Junior Member
Join Date: Sep 2006
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Oct 19, 2006, 07:22 PM
I really don't recommend this. If you have an extra HD, install it, but don't use it for work.
Mac Elite
Join Date: Aug 2005
Location: Vancouver, BC
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Oct 19, 2006, 07:52 PM
As a sidenote, that site overall seems a bit fishy to me. I like how the part about their programming contest that is only open to PAYING members and whereby they will ultimately own the source code and all distribution rights for all software that is submitted for the contest. At least they're honest about it i guess...
Mac Elite
Join Date: Apr 2000
Location: Minneapolis, MN USA
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Oct 24, 2006, 04:33 PM
I'd also be very careful about overclocking a non liquid cooled machine
to speeds close to the 2.5/2.7 G5 units because with no liquid cooling,
the processors and the memory controller in particular are going to be
hot enough to cook an egg on.

My 2.5 dual (liquid cooled) has seen temps on the backside of the
memory controller in excess of 213 degrees. I do not exagerrate in
saying that if you push a non-liquid cooled machine to similar speeds
you could very well end up with a superheated pile of slag in your
computer room.

Also, if your machine is under warranty it certainly has been voided
by such modification.
Fresh-Faced Recruit
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Oct 25, 2006, 02:09 AM
??? My CPUs are currently running @ 116F and 122F. I've seen them as low as 95F and 97F on a 2x2 rev.A G5. That's pretty cool by PC standards.

The U3 reports as 138F. Definitely would be hot to the touch, almost burning, but not outrageous.
If engineers ruled the world, the trains might not run on time, but they'd go really fast, and when they derailed, would explode and kill thousands!
Mac Elite
Join Date: Apr 2000
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Oct 26, 2006, 04:40 PM
Dual 2.5 reaches 160-170 degrees fahrenheit in the CPU department routinely
while running Seti @ Home.

Backside of memory controller is generally not at 213 f all the time but
sometimes reaches it under heavy load.
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