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View Full Version : Power consumption of 7457 compared to other processors


baytch
Sep 16, 2003, 03:52 PM
I am a physics grad student with an old clamshell iBook, and am looking to get a new laptop. I had thought that the 7457 was supposed to consume less power than the 7455 but then I looked at:
http://e-www.motorola.com/webapp/sps/site/prod_summary.jsp?code=MPC7455
If you look at the pdf file MPC7455EC under data sheets, and then look at the analogous info for the 7457 link:
http://e-www.motorola.com/webapp/sps/site/prod_summary.jsp?code=MPC7457
you see that typical power consumption of the 7457 at 1 GHz is 15.8 watts, while typical power consumption of the 7455 at 1 GHz is 15.0 W. [Oddly, Motorola claims on the webpage that the 7457 "dissipates less than 10W while running at 1 GHz." The pdf file spec sheet indicates that the 7457 dissipates less than 10 W only if it's sleeping!]

I'm not interested in getting a laptop that will toast my lap, and furthermore, I think that having a more efficient processor is just better in general. I know that Motorola is behind the curve here, but I'm curious how the 7457 power consumption compares to the Intel Pentium M [Centrino]. I had difficulty finding this on Intel's site. Not that I'm planning to go over to the dark side, but I'm thinking of waiting until the processors in Apple machines have caught up. I tried to find the power specs on G3s. All I could find was:
http://www-3.ibm.com/chips/products/powerpc/newsletter/jun2003/newproductfocus.html
which indicates that the upcoming G3 will dissipate less than 8W at 1 GHz. Maybe I should wait for the iBook updates...? I'm not exactly a power user -- beyond web browsing, I guess the most processor-intensive thing I do is Mathematica. I burn CDs occasionally too. My concern with the G3 is that in 3 years, new applications will require at least a G4.

bousozoku
Sep 16, 2003, 04:13 PM
Those nominal figures most likely do not account for the AltiVec unit running at all. I would expect that the 7457 exceeds 24 watts, and the 7455 2-3 more.

You're right about the AltiVec-enhanced software. In a few years, all software should be using it along with software coming on DVDs. Still, the iBooks may still come in the current G3 form with a "new iBook" to replace it in the way that the iMac was replaced.