• Core i7 in MacBook Pro Hot Enough to Boil Water

    The new Core i7-equipped MacBook Pro model may have a heat buildup issue, if a recent set of tests hold up. The Australian PC Authority magazine ran a series of benchmarks on the new notebook and found that when pushed to the limit, the processor reached an alarming 101C - above the boiling point of water - and the bottom of the laptop was uncomfortably hot to the touch. A side-by-side test with a Fujitsu laptop running the same test showed it running as much as 20 degrees cooler, raising questions about the way the high-performance Core i7 processor was incorporated into the existing chassis of the MacBook Pro.

    PC Authority was putting the new top-of-the-line Apple notebook through its paces, and in the process of running its normal benchmark suite, they noticed that the MacBook Pro was seriously underperforming at some Photoshop tasks. Guessing it might be a heat-related issue, they turned the computer on its side and found it performed much better. The design of the MacBook Pro's aluminum unibody uses the case itself to aid in heat dissipation, and ordinarily it works very well, with the aluminum of the enclosure radiating the heat out to the cooler ambient air. In this case, however, the PC Authority testers theorized that the heat wasn't being reduced effectively enough.

    They decided to see how the MacBook Pro handled heat at full load, and booted the computer into Windows in order to do some rendering in Dwarf Fortress. After a few minutes, the CPU had shot up from an idle temperature 50C (or 122 in the quaint Fahrenheit temperature scale we use in the United States) to 84C, or 183F. They drove the processor through some even more intensive runs with the Cinebench multi-threaded 3D rendering benchmark tool, and succeeded in pushing processor temperature to 95C or 203F. Repeating the same test in OS X raised the temperature to 90C, and though the sensors on the bottom of the case only registered a slightly warm 39C (102F), the testers reported that the underside was "almost too hot to touch." After letting the MacBook Pro cool overnight and doing the tests again, temperature reached 101C (213F) on the second Cinebench run.

    They did the same battery of tests with a Fujitsu Lifebook SH 760, which uses the same Core i7-620M CPU as the MacBook Pro. The plastic-bodied Fujitsu, however, has a copper processor heatsink that vents out the side, rather than the bottom. The Fujitsu's CPU went from an idle temperature of 40C to a maximum of 81C after three Cinebench runs. The team also reported that the Fujitsu was cool to the touch.

    Intel's specs indicate that thermal max for this chip is 105C. While the high temperatures were the result an intentional stress test to run the chip as hot as they possibly could, it's not common to get that close to threshold temperatures in any controlled testing. The processor's overload circuits may even have kicked in (at least one hopes so). And the PC Authority guys point out that they did a lot of real-world tests that caused temperatures to spike.

    Even more worrisome is the reported high temperatures on the bottom of the case. Probably not a good idea to do a lot of rendering with a Core i7 MacBook on your lap...
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