[Ti] Design and/or heat dissipation issues?

[Chris Olson]

On Dec 4, 2004, at 5:26 PM, Adam Boettiger wrote:

> You mentioned that the cooling issue won't be fixed until they start 
> using faster chips, which might be ... When?

The faster the chip's clock speed, the hotter it runs.  The die size 
makes a significant difference.  The current 130nm process MPC7447A 
(G4/1.5 GHz) dissipates ~36 watts.  Freescale (Motorola's semiconductor 
division) has a new 90nm process MPC7448 that dissipates 10 watts at 
1.4 GHz.  The MPC7448 is pin-for-pin compatible with the current 
MPC74xx processors, and I suspect it will be the next cpu used in the 
PowerBook.

> Or is it possible that by the time they start using faster chips there 
> will be a newer OSX that uses those faster chips, so the heating issue 
> may always be a problem?

The processor isn't the only thing that creates heat.  The faster the 
bus, the more heat you get from the logic board.  The faster the RAM, 
the more heat it creates.  The faster and larger the hard disk, the 
more heat it creates.  The more video RAM you have and the more 
powerful the GPU, the more heat you get.  The AirPort card, ethernet 
interface, modem, power supply, and even the optical drive all create 
heat.

The PowerBook is very thin with a metal case so you feel it get hot.  
If you compare with PC laptops, such as the IBM Thinkpad, the PC is 
thicker and they have more room to use a copper heat duct and sink, and 
air baffle to quiet it down.  They also have room to insulate it so you 
can't feel the heat on the case as much.
--
Chris