User profile for user: heycarlos
heycarlos Author
User level: Level 1
4 points

ZDNet: New Utlity to Overclock Mac Pro

Well, they claim you can OC a 2.8GHz mac pro to 3.2GHz safely using this utility.

I've downloaded the app and will post results as soon as I can.

One caveat -- no performance improvement in Xbench (or other benchmarks) but the article seems to address this and suggests a stop watch to see the real-world performance gains since the Mac clock is tied to the system clock.

From the article:

+Unlike Windows, Linux and many Hackintosh versions, Mac OS uses the bus clock speed as the time source. It is compared with real time when booting up. Nor does time correction by means of the Mac OS NTP daemon succeed: It simply no longer works with a large discrepancy between the bus clock and real time.+

+Whereas programmers of the IBM PC XT had to be forgiven for using the bus clock speed because of inadequacies of its Intel 8253 timer module, it should be reasonable to expect more from Apple, who now only offer computers with modern HPET timers. After all, multimedia applications use the HPET module. So videos do not run faster after overclocking.+

+The only option for "normalising" the time of the Mac Pro again is to restart without switching off the computer. ZDNet Clock is fundamentally "reboot-proof". But there are a few snags. The latest series of the Mac Pro (Mac Pro 3.1) can indeed be overclocked in the ZDNet test up to 3241 MHz while remaining stable. But a reboot without crashing is only possible up to 3178 MHz. Carefree overclocking fun does not exist beyond this frequency.+

Here is the article and download to the utility:
http://www.zdnet.de/enterprise/mac/hardware/0,39038647,39192217-1,00.htm

Mac Pro 8-core 2.8GHz, Mac OS X (10.5.3)

Posted on Jun 27, 2008 9:22 PM

Reply
33 replies
User profile for user: Philip Scherzinger
Philip Scherzinger
User level: Level 1
5 points

Jun 28, 2008 7:16 PM in response to heycarlos

I have a Mac Pro 2.66GHz (MacPro1.1). I do indeed suffer the problems not being able to reboot when changing the clock speeds, but I still did some testing with this tool.

I was surprised that I am able to clock this computer up to 3.20GHz while being incredibly stable and reporting no parity errors. I could even clock it up to 3.28GHz which is the max and there are no sudden kernel panics, just some parity errors on one of the memory modules I installed.

I have 6GB of RAM, with 2GB originally coming from Apple.

This looks promising and I look forward to future updates. Glad to see that the newer Mac Pro's have success even when rebooting.
Reply
User profile for user: Matthias Wahl
Matthias Wahl
User level: Level 1
100 points

Jun 29, 2008 11:50 PM in response to heycarlos

I have the "Original" 8-Core Machine (MacPro 2.1) with 3.0GHz.

Runns fine till 374MHz (Bus Clock), 1.498 MHz (MB Clock) and 3.374 MHz (CPU Clock). But I'm not able to reboot at any speed but the original one 😟

I use 4GB Apple RAM... an wondering if it could be possible to use the (new) 800MHz RAM as well...? Maybe this would solve the problem...? At least could give me a higher range to overclock my Bus Clock...!?

Does the new RAM work with my machine, or am I stuck with the 667MHz models...?
For example - my old G4 500 Dual uses 100MHz Bus Speed and works well with 133MHz RAM...
Reply
User profile for user: lunelson
lunelson
User level: Level 1
0 points

Jun 30, 2008 6:37 AM in response to Philip Scherzinger

Hi Philip,

I have the same model as you (Quad 2.66, MacPro1,1), I read the notes on ZDNet and I'm curious about what this means "not being able to reboot" --

does it mean that once you overclock, the reboot command doesn't work? Or that it causes a crash?

Are you forced to do a hard shutdown each time (pressing and holding the power button)?

If one has to do a hard shutdown then I guess I can't use it. It will throw all my RAID 1 volumes out of sync.
Reply
User profile for user: The hatter
The hatter
User level: Level 9
61,031 points

Jun 30, 2008 7:10 AM in response to lunelson

http://www.hardmac.com/news/2008-06-30/#8515I would restart before using it in Safe Mode, to make sure everything is clean and as few startup and background processes run.

I didn't follow my own advice and ended up having to spend an hour with Disk Utility and Disk Warrior cleaning up my own mess 😟

.... but, it did run, and I could inch it up ever so slightly, not enough and obviously not something I'll do again for awhile.

http://www.hardmac.com/news/2008-06-30/#8515
Reply
User profile for user: kentech
kentech
User level: Level 1
1 points

Jun 30, 2008 12:25 PM in response to heycarlos

Christopher, thank you for this smartly-designed utility. But before I experiment anywhere near the edge for my 2.8 MHz 2008 Mac Pro, I would love to understand a couple of things:

(1) Over a warm Restart, or alternately a cold boot, how are the overclocking parameters retained (or not)? Is the kext in the temp directory the source? Do the parameters NOT survive a cold restart. Which leads to . . .

(2) If one goes a bit to far out on that limb and the Mac goes wonky, how does one safely reboot into the original speed settings? I.e. how does one recover instead of another reboot into a crash? Or do the parameters NOT survive a cold reboot?

Is that why the overclock.kext is in the private/temp/ directory? Does it get deleted on cold boot?

I guess a little more detail about the locations and inner workings of the utility's generated files would be nice to have and would increase my confidence.
Reply
User profile for user: Philip Scherzinger
Philip Scherzinger
User level: Level 1
5 points

Jun 30, 2008 7:36 PM in response to lunelson

Lunelson,

Once you overclock and reboot, the power light will flash rapidly and will not start up. You have to hold to power button to manually shut off the computer. Once you do this, your computer will start up normally, but the clock speed is reset back to default settings, which is 2.66GHz for you and me.

Only the newer Mac Pro's which were released in early 2008 will be able to reboot, as of now. I saw some mention of the author of this program looking into a fix for our models?
Reply
User profile for user: TV Pete
TV Pete
User level: Level 1
55 points

Jul 1, 2008 2:18 AM in response to heycarlos

I tested this interesting little utility earlier, but unfortunately my Mac won't go above 2.84GHz before it falls over. I have tried this 4 times and the second time it froze at just 2.828GHz. The other failures consisted of the screen greying from the top, and the machine informing me it would need to be restarted. The fourth attempt I increased the fan speed to 50% (extremely noisy in the very quiet environment I live in!), and it went to 2.842GHz before it just froze.

I was running the console throughout, and saw no warning of the impending failures.

I have 8 x 1GB RAM, so all 8 slots are filled, and the utility I run under widgets always shows significant temperature differences between the memory slots, not huge, about 20ºF. The memory consists of the 2 original Apple 1 GB sticks and 6 x 1GB from OWC.

P.S
If it's not clear, this is the Jan 2008 model MacPro3.1!
P.P.S
I'll try taking out the extra memory later today and retesting to see what happens

Message was edited by: TV Pete
Reply
User profile for user: ZDNet Clock
ZDNet Clock
User level: Level 1
0 points

Jul 1, 2008 4:29 AM in response to kentech

kentech,

the kext, which does actually modify the clock chip's frequency, will only be loaded, when you start ZDNet Clock. Neither a warm nor a cold reboot will cause the kext to be loaded, because private/tmp gets deleted, when you reboot.

This means, for a warm reboot your machine is still overclocked, because BIOS/EFI don't touch the clock chip on a warm reboot. A cold reboot (shutdown, plugging out the power cord, etc.) always causes the machine to run at stock speed again.

We also created a FAQ on topics like this based on the feedback we got. You may want to look at http://www.zdnet.de/enterprise/mac/hardware/0,39038647,39192217-5,00.htm

-Christoph
Reply
User profile for user: The hatter
The hatter
User level: Level 9
61,031 points

Jul 1, 2008 5:01 AM in response to ZDNet Clock

One comment, based on my MacPro1,1
*Are there any risks involved in overclocking by a great deal?*
As with any system crash, you lose unsaved files. Since HFS+ is a pretty robust filesystem, it recovers well at the next reboot.

I was surprised because I had a clean system and had run DU and Disk Warrior earlier, and had not had any problems (for months, since last fresh install). In fact, I had cloned my system, run DW etc all in getting prepped for 10.5.4.

No other programs were loaded or running except System Profile (I wanted to watch for memory or parity errors). Probably should have restarted the Finder or done a sync command to flush changes to files and directory before running. My directory had some orphan files and needed to be repaired with both Disk Utility and Disk Warrior.

I don't consider OS X filesystem to be all that robust, nor does Disk Utility look to see all the possible problems, which is why you still must use 3rd party tools (MicroMat, Alsoft, etc). It is also possible for the journal to become corrupt and need to turn off, then turn it back on (booted from another drive) to get it back to working.

Of course the best course of action is to restart before using any utility like this, and do your testing on a drive other than your normal boot drive that you use for regular work and use.

So my own feeling is that HFS+ is a little less robust, a little more fragile.
Reply

This thread has been closed by the system or the community team. You may vote for any posts you find helpful, or search the Community for additional answers.

ZDNet: New Utlity to Overclock Mac Pro

Welcome to Apple Support Community
A forum where Apple customers help each other with their products. Get started with your Apple Account.
Learn more Sign up