MBP C2D Issue?

[andy-ch]

I heard a rumor that if we're running MBP without a battery (by directly plugged into the electricity socket) the MBP C2D will run only 1 core, and not 2 cores. So the power/speed/performance is divided by half percent!

Has anyone here encountering this rumor?

 

[Scarlet Fever]

when i take out the battery from my CD MB and run it off the wall it runs at 1GHz, but still uses both cores. What does it matter anyway?

 

[iW00t]

Why are you so adamant about running a laptop as a desktop?

For the price of a MBP you can buy an iMac and a Macbook, make up your purchasing decisions with that as your basis.

 

[andy-ch]

I just heard from my friend, that if he took off the battery, and plug the MBP directly to the electricity socket, the MBP runs only 1 core which causing the performance is divided by half.

 

[e12a]

eh, do you guys know what Duo-Core means? or the purpose of 2 cores?

1 core doesnt necessarily mean half the speed. its not like 2.33 = 1.65 GHz computer with 1 core...Doesnt work that way in general.

but yes, in the case of the Macs, it does underclock itself

 

[deadpixels]

if it runs two cores @ 1ghz or one core @ 2ghz, isn't that the same?

 

[e12a]

if it runs two cores @ 1ghz or one core @ 2ghz, isn't that the same?

no it isnt.

you dont simply add up the speeds for a dual core system.

what would that make a quad core now? With this thinking, that would make a Quad Core Mac Pro run at 750 MHz (3GHz) on one core. Surely the 1.65 GHz core of the MBP (2.33 GHz) is more powerful? Its almost one whole GHz greater!

 

[siurpeeman]

i didn't know macbooks ran at 50% without a battery, but who uses their laptop w/o a battery? also, if the laptop is plugged in, why is there the need for power saving?

if it runs two cores @ 1ghz or one core @ 2ghz, isn't that the same?

depends on the app now, doesn't it?

 

[gr8tfly]

Just unplugged and on battery. I'm running Toast, encoding a DVD. It's using both cores (using top, seeing up to 194%), and running 2.33GHz. Using Hardware Monitor app to graph frequency - it's pretty solid on 2.33GHz even as I type this.

Power management will try to reduce CPU frequency, when it's not needed, and the priorities are different when running on battery. But, when you need it, you will still get full speed.

17" MBP C2D

 

[e12a]

Just unplugged and on battery. I'm running Toast, encoding a DVD. It's using both cores (using top, seeing up to 194%), and running 2.33GHz. Using Hardware Monitor app to graph frequency - it's pretty solid on 2.33GHz even as I type this.

Power management will try to reduce CPU frequency, when it's not needed, and the priorities are different when running on battery. But, when you need it, you will still get full speed.

17" MBP C2D

I think the whole purpose of this thread was on running off the wall with the battery removed...try that.

 

[gr8tfly]

Oops, I did miss that point. Just pulled battery.

So, big surprise to me - it really is running at 1GHz! Bizarre.

However, it is still running both cores. (same percentage for Toast as before)

Have to do some reading up on the reasoning behind this, but I imagine it has to do with the MBP's power supply.

 

[deadpixels]

no it isnt.

you dont simply add up the speeds for a dual core system.

what would that make a quad core now? With this thinking, that would make a Quad Core Mac Pro run at 750 MHz (3GHz) on one core. Surely the 1.65 GHz core of the MBP (2.33 GHz) is more powerful? Its almost one whole GHz greater!

i must have missed something here, each core on the mbpro 2.33ghz are only 1.65ghz??? i thought each core was 2.33ghz
still two cores running at half speed or one core at full speed, wouldn't that be the same theorically?

 

[gr8tfly]

Both cores run at 2.33GHz (max), but I think the point is you don't get the equivalent of 2x 2.33GHz. Even in the best case, there is overhead in the OS, so a single app/thread can't get 200% total. Very dependent on the application design, and how its tasks are distributed among threads.

 

[e12a]

i must have missed something here, each core on the mbpro 2.33ghz are only 1.65ghz??? i thought each core was 2.33ghz
still two cores running at half speed or one core at full speed, wouldn't that be the same theorically?

i think you misunderstood my previous post. I was giving an example of how the OP would think, if one were to simply multiply the cores' GHz and # of cores together and present it as whole. I know they dont run at 1.65 ghz each. Both cores run at effective 2.33 GHz.

Their performance doesnt necessairly "add" up. Unless its running an app designed for multiple cores. A single Pentium 4 can run faster than a equivalent computer with multiple cores for example, if the game or app wasnt designed for a multi core application. Think of the cores performance as working in tandem, rather than stacked.

 

[andy-ch]

so MBP must use it's battery for it's maximum performance?

 

[gr8tfly]

Here's Apple's KB on this (just came out today):

http://docs.info.apple.com/article.html?artnum=305336