MacBook Pro: How Does Steve Jobs Measure That 4x Performance/Watt Thingy
ZDNet has published a psychic review for the most talked-about gadget on the planet so far this year. It’s quite amazing how people can review something without getting their hands on the reviewed stuffs these days. That’s why I call it a psychic review. Anyway, the downside part of the review is particularly interesting, because ZDNet really looked into something of paramount importance in mobile computing, but yet was constantly overlooked during the hype surrounding MBP for the past week: how long can the juice stand.
Whilst Jobs neglected to mention the battery life in his keynote, he did leave a couple of hints for us to decipher: MBP will deliver performance that’s 4x faster, and 4x as much performance per watt as the PowerBook G4. The question is, how did his underlings come up with those numbers? If you think really hard with the GOL (good old logic), you will come up with an answer like this: battery in MBP unit may be the same battery unit as the one in PB G4. And if you come up with that answer, ta-da, you’re right! Steve Jobs confirmed it in his interview with Newsweek. Here’s the excerpt:
How is battery life with the MacBook?
About the same—this with a dual processor [chip]! Each processor is as fast as a G5, and the battery life will be the same as [the previous PowerBook’s] G4.
Of course! What’s the unit normally used for measuring battery capacity? mAH, AH? mAH stands for milli-ampere-hour and AH stands for ampere-hour, which measures the amount of electricity current flowing for one hour. Electronics 101: watt is the unit for power, and the relationships between watt and ampere is P = VI (P = Power, V= Voltage, and I = Current). So if you take out V (Voltage) by assuming that output voltage is equal, then P will be proportional to I. In English, the fact that MBP performance is roughly 4x as much as PB G4 (that’s from the SPEC benchmarking performed by Jobs’ underlings), 4x Performance/Watt really means 4x performance out of the same amount battery juice. You can’t come up with 4x Performance/Watt if the batteries used in MBP and PB G4 are different.
Disappointed? Uhmm, hell yeah…, no.1 rule for mobile computing is longer battery life, and it must be respected.