G5 Lifespan and 'throttling?'

[Johnny]

I read a comment elsewhere that throttling is common in higher-freq chips...that the G5 won't run at full-tilt 100% of the time, and to disable this throttling was a sure way to reduce the life span of the CPUs..

anyone know about this?

J

[Ade]

Powerbooks have had this forever...
I noticed that when i checked out the 1,8 version in system profiler it said it had a 900mhz bus..I said to myself wasnt it 1000mhz?

[Antimatter]

it might be different inregards with the macs but in my option throttling is bull****, its good for like laptop that are having overheating problems but still... ive had several PC running at full blast folding @ home and SETI and few other project for the past what good 5-8 some years from this ancient 233 mhz etc... and guess what theyre all overclocked from 5% to 40% overclock and still going strong so, i have little bit of heating problem but with a little bit of cash i fixed it pretty much for good :) and theyre still doing just fine, not a single glitch, i had fun setting the network up but onice its up it has been running seady for what good 2-8 some years depending on which computer youre talking about :)

anyway now with regards with mac i ditto, now it might make sense on my old laptop or laptops with heat problems but on a desktop pc that is well designed i think its a bunch of bull imho. but that's just me that's all.

[serpicolugnut]

I noticed that when i checked out the 1,8 version in system profiler it said it had a 900mhz bus..I said to myself wasnt it 1000mhz?

No, the bus runs at 50% of the CPU speed. So, the 1.6ghz runs at 800mhz, the 1.8ghz runs at 900mhz and the 2.0ghz runs at 1.0ghz.

So a ASP reporting a 900mhz bus on a 1.8ghz is correct...

[Lynx3d]

Well in Notebooks the throttling is just to save battery power...shouldn't overheat at full speed of course, that'd be pretty crappy...
Donno about iBooks or Power Books, just know my Pentium-M, it clocks itself in 200MHz steps down to 600MHz, depending on workload. You don't really notice that, because if you need mor power, it clocks up to its 1.5GHz again. But it saves quite a bit of battery time...

I really can't believe a G5 needs throttling to enhance its own lifespan...unless it's some kind of overheating protection (Pentium4 does that...but obviously you want to prevent overheating)
Where did you read that?

[Beamtracer]

Interesting news on MacCentral that relates to this.

http://www.macworld.com/2003/09/reviews/macworldlabfirstg5testresults/

They benchmarked the 3 new models of G5 computer against each other. And guess what... this throttling made a difference to the benchmarks:

"In an interesting quirk, we found some dramatic speed differences in these systems depending on how we set the new Processor Performance preference, found in the Energy Saver pane of System Preferences. By default, Processor Performance is set to Automatic. Changing the setting to Highest improved our results quite a bit. Our MPEG-2 compression test, which took 9:44 on the 1.8GHz system at the stock setting, took 8:32 at the Highest setting. Overall Speedmark scores on the 1.8GHz system rose from 214 to 225 when we switched from Auto to Best."

If anyone takes delivery of a new G5 they should remember this before posting benchmarks on the Blanos website.

[Johnny]

Originally posted by Beamtracer
we found some dramatic speed differences in these systems depending on how we set the new Processor Performance preference...by default, Processor Performance is set to Automatic. Changing the setting to Highest improved our results quite a bit.


makes me wonder why throttling isn't 'Smart,' ie...why it doesn't sense the need for more computational horsepower, then provide it.

So, if we keep the setting at Highest, are we dooming our chips to premature death?

J

[Beamtracer]

I think what you call "throttling" is the same thing others are calling "bus slewing". There's a recent story on the MacRumors website that gathers together some links on this:
http://www.macrumors.com/pages/2003/09/20030907030313.shtml

Included is a quote from Apple's developer documentation:

To lower power consumption, heat generation, and fan noise, the Power Mac G5 computer incorporates an automatic power management technique called bus slewing. Bus slewing is designed to run at high processor and bus speeds and high voltage when the demand on the processor is high, and to run at low processor and bus speeds and low voltage when the demand on the processor is low.

Also included is this quote from Ars Technica that says there will be no performance loss from bus slewing:

The ramp time up or down is ~1ms, but the CPU is running normally during this time, so there is no performance "hiccup". This results in about 60% power/heat savings, which jumps up to about 85% savings if the machine is idle and they "turn on other power saving features". When idle, the CPU fans are barely turning.

However, recent benchmarks suggest that bus slewing will affect performance.

[Ade]

Does the DP 2ghz have a true FSB as in 2x 1000mhz buses or is the 1000mhzbus cut into two 500mhz paths?

[Johnny]

Originally posted by Ade
Does the DP 2ghz have a true FSB as in 2x 1000mhz buses or is the 1000mhzbus cut into two 500mhz paths?

good question...I wanted to know, too, as I'm waiting on a Dual 2...

There's a Tech paper in pdf form you can download here:

http://www.apple.com/powermac/performance/

Yes, each chip DOES have it's own dedicated bus...the PDF spells it all out.

Johnny

[Ade]

yes but at wat speed? 2x500mhz or 2x1ghz?

Judging by the macaddict tests g5's fly with more ram.

[Johnny]

Originally posted by Ade
yes but at wat speed? 2x500mhz or 2x1ghz?

Judging by the macaddict tests g5's fly with more ram.

to quote the PDF:

3 Dual independent 1Ghz frontside buses. In dual PowerPC G5 systems, each processor has its own dedicated frontside bus...

each chip has its OWN bus, and each of those bus speeds is 1Ghz.

[gggraphx]

Ain't the durn thing gonna be junk in 2 years anywho?
I say crank the sucker and you might actually be able to use the Applecare you buy.

[Johnny]

Originally posted by gggraphx
Ain't the durn thing gonna be junk in 2 years anywho?
I say crank the sucker and you might actually be able to use the Applecare you buy.

heh! I dunno...I'm using a DP 450 now, and tho it's by far not the fastest box out there, it's extremely capable..I don't really feel denied that often, except in LW or FCP...but for most things, it's a real workhorse.

I think the G5 will enjoy an even longer life because of its larger capacity...but I'd think that after 5 years, a machine doesn't owe you anything...more than that is gravy.

J

[gggraphx]

5 years. Dang, the wife has the last computer by year three if that. Your point is well taken tho...they do keep on tickin'. And if you do this stuff for a living then it pays for itself pretty quick. If I get a G5 I'll do what I always do with Macs...get the fastest, baddest one and max the RAM then, bang-boom to the moon. Oh yeah, and the wife will get the last one.

[Beamtracer]

Apple has now basically admitted that the automatic energy saving feature called "bus slewing" can slow down your performance on a G5 computer.

Apple has posted a technical notice to users of its compositing software, Shake. The notice advises Shake users to turn off automatic "bus slewing" in the Energy Saver contol panel. It would be interesting if this advice is also relevant to Lightwave users who are prepared to use more electricity to get a speed advantage.

Apple's advice to Shake users:
http://docs.info.apple.com/article.html?artnum=93448
DISCUSSION
When using Shake 3 on a Power Mac G5 computer, Energy Saver should be configured using the Highest performance option.
Follow these steps:

1. From the Apple menu, choose System Preferences.

2. From the View menu, choose Energy Saver.

3. Click Options.

4. From the Processor Performance pop-up menu, choose Highest.

[Beamtracer]

Energy Saver Control Panel:

[Johnny]

as we suspected, but now I wonder about something...

6 cooling zones, 9 fans, hundreds of little holes to pass airflow...makes me wonder why the G5 Energy Saver panel offers a Reduced setting.

I could see it in the case of G5-based Powerbooks, but as of now, there is no such beast available to consumers..

J

[nawDsign]

I just did a quick test on one of my scenes with tons of reflection and raytracing. On highest setting it rendered at 64.9sec, 65.2 on auto, and 97.3 on Low. i'm thinking I'm keeping it at highest! If it craps out oh well, for now I'll enjoy the speed and listen to the calm and serene fan sound just like the ocean waves.. speaking of which, they just kicked in right now. hehe

Nor

[lonestar1]

Originally posted by Johnny
makes me wonder why throttling isn't 'Smart,' ie...why it doesn't sense the need for more computational horsepower, then provide it.

It does. When you start a render with multithreading, you can hear all 9 fans coming online as the processors start to work at full speed and put out more heat. It sounds like an airplane warming up for takeoff.

So, if we keep the setting at Highest, are we dooming our chips to premature death?

No, it simply increases the energy consumption and possibly your electric bill. I say possibly because if it's winter and you heat your house with electricity anyway, all you're doing is diverting some of the electricity -- it ultimately turns into heat either way.