AMD's PowerNow Technology: A Must Have for DVD
Oct 02 '00 (Updated Oct 08 '00)
Buying a laptop for watching DVD movies, presumably on those long, boring flights where the only film being shown is garbage you wouldn't even pay a buck to see, is a rather interesting proposition.
On one hand, DVD decoding is one of the most CPU-intensive tasks imaginable, and most likely the single most hardware-intensive task you'll ever do on a laptop. Decoding an MPEG-2 signal in software, and maintaining a smooth 30 frames per second in even the most chaotic scenes, is enough to choke almost any older laptop. If you really want to have the best DVD quality in your laptop, you'll need to go with the most powerful, power-hungry beast you can find.
On the other hand, if you bought one of those power-hungry beasts of a laptop, good luck watching more than one movie (if even that) before your laptop goes dead in midflight. Better hope that in-flight movie's at least halfway decent...
Indeed, power vs. battery life has been one of the major tradeoffs that laptop manufacturers must make when designing mobile PC's, and it's also a major issue that consumers must face when choosing which laptop to buy. Although newer laptops will typically incorporate the newest advancements in battery technology, with the latest power-draining active matrix screens, powerful video chipsets, and CPU's clocked at very high frequencies, a solution is sorely needed to conserve battery life without severely compromising performance.
Enter PowerNow Technology
AMD's solution to that quandary is PowerNow, a technology built into all their current mobile CPU's (currently the K6-2+ and the K6-3+). PowerNow will automatically "throttle" your CPU, going between any of 32 speeds and power levels, depending on how much processing power is needed at any given point in time. Those speeds range, in the case of the K6-2 550, anywhere from 200 mhz in its lowest-power mode to 550 mhz in its full power mode. In other words, if you're just tying up a Word document it will only consume as much power as necessary, by throttling the CPU back to 200 mhz and conserve battery life. But the instant you load up a more complex application like Photoshop, it will instantly increase the processor speed to allocate as much power as Photoshop needs.
But the beauty of PowerNow is that it can continuously and seamlessly go between its 32 different speeds. That means it doesn't just increase power when you load Photoshop, then decrease power when you close Photoshop. It can actually dynamically allocate power "on-the-fly", so that you're always getting as much CPU power as you need at any given point in time, and use only as much battery as it needs to.
So how does this help with DVD movies?
Coincidentally enough, DVD playback is the perfect application to demonstrate the benefits of PowerNow. DVD playback is perhaps the only application where:
1) CPU requirements are very high overall
2) CPU needs fluctuate greatly from one moment to the next
3) Those needs must at least be met at all times, or noticeable "stuttering" will result
4) The application needs to run for at least 90 minutes continuously (typical length of a film), and sometimes as long as 3 hours
#'s 1, 3 and 4 are obvious, but #2 might require some explanation of how software DVD playback works. The way movies are stored on DVD is in "MPEG-2" format. What that means is that each "frame" of animation is not stored separately, and when you watch the movie it's not as if it's simply playing all the frames one after another. Instead, the DVD stores the information of what changes from one frame to the next, and the CPU only has to "update" the changes to the screen. It's a very active process that requires the CPU to "decode" the signal continuously as it's being read off the disc.
So if you're watching a scene where it's just some guy sitting against a plain background, very little updating is going on (maybe only the guy's head, and a few other things that change very slightly from one frame to the next). As a result, playing such a scene requires minimal CPU power. But if you're watching an extremely chaotic war scene with the camera panning across the action, it's possible that every single pixel on the screen is changing from one moment to the next. It's scenes like that which tax a processor to its limits, or else "jerky" video will result.
It's obvious that PowerNow directly addresses all four of these issues relating to DVD playback. By providing as much CPU power as is needed for any given point in the movie, PowerNow laptops can provide smooth DVD video while keeping battery usage to an absolute minimum, and enabling the user to watch more DVD movies before running out of juice.
Anandtech.com recently released the first review of a PowerNow enabled laptop, the Hewlett Packard Pavilion N3370, and the results were impressive (article can be found at http://www.anandtech.com/showdoc.html?i=1318 ). Battery power overall was increased by 21% with PowerNow enabled in "automatic" mode (allowing the CPU to change speeds automatically), from 127 minutes to 154 minutes. Perhaps more importantly, the performance drop-off in their tests was typically only 0-10% depending on the application, compared to the same laptop with PowerNow disabled. Running the laptop in "max battery life" mode, which basically means the CPU is set to 200 mhz (the ideal setting if you are simply typing documents, for example), yielded 37% more battery life (174 minutes), although that setting would not be suitable for DVD playback for obvious reasons.
What about Intel?
Intel beat AMD to the market with their own Speedstep technology, which has similar goals of extending battery life by slowing down the CPU. Pentium III latpops incorporating Speedstep have been on the market for some time, with PowerNow laptops just now being released by companies such as HP, Toshiba, Compaq, Fujitsu, NEC and Sharp. However, the differences between Speedstep and PowerNow are night and day, with AMD's PowerNow being the superior technology by a wide margin.
Whereas PowerNow has 32 different levels of power consumption available, Speedstep CPU's only have two: maximum and low (although it should be noted that it's up to the laptop manufacturer to determine how many of PowerNow's levels are actually used; the first batch of PowerNow laptops only use four of those levels). And whereas PowerNow dynamically detects CPU needs on the fly, Speedstep can only detect whether the laptop is plugged into a wall, or if it's not.
And although Speedstep's purported goal is to conserve battery life, by looking at the difference between "maximum" and "minimum" it becomes apparent that not a great deal power is being conserved. The low-power mode for the 600 and 650 mhz PIII's is still 500 mhz; 750 PIII's go down to 550 mhz, and 850 mhz PIII's go down by only 100 mhz to 750 mhz when in power-saving mode. Although it's certainly a great benefit compared to nothing at all, when one realizes how very little CPU power is required, say, while writing an article for Epinions, that's still quite a bit of battery power going to waste. In such a situation, the ability of the CPU to throttle back lower into the 200-300 mhz range could be of great benefit.
It should also be noted that Intel has come under criticism for only packaging Speedstep technology in their high-end mobile Pentium III chips, and not in their mobile Celerons (even though there is no technical reason for doing so), whereas AMD's plan from the beginning has been to incorporate PowerNow in all their mobile CPU's. Of course, recent reports suggest that Intel will soon give mobile Celerons Speedstep as well in response to PowerNow, although that has yet to be confirmed.
To quote British IT news site The Register, who recently did a story on PowerNow! vs. Speedstep, "AMD's PowerNow technology is so far ahead of... Speedstep as to make Intel look very second rate indeed."
But aren't PIII's more powerful than K6-2's?
Yes, but one must wonder what kinds of applications will be run on a laptop that actually require more CPU power than a K6-2+ or K6-3+ provides (and more CPU power than DVD playback requires, for that matter). Nonetheless, if you're looking for a PowerNow enabled laptop and simply must have the most powerful CPU available, mobile Athlon and Duron laptops will be available by the end of the year, with 1 ghz models appearing in early 2001.
Interestingly, mobile PIII's are expected to remain in the sub-ghz range for quite some time. Recent road-maps do not show Intel cracking the 900 mhz barrier in mobile CPU's until the 2nd quarter of 2001. If AMD does indeed release 1+ ghz mobile chips early next year, the fastest mobile CPU's available will be non-Intel for the first time.
Conclusion
Once more reviews of laptops supporting PowerNow are released, I'll be updating this article with those results. It will be helpful to compare the battery life of several models to get an better idea of PowerNow's benefits, since even on similarly configured laptops, battery life has historically varied significantly from one model to the next. Of course, the statistics of the HP Pavilion laptop are encouraging, and hopefully the rest of the first PowerNow enabled laptops will also live up to their promise, and finally provide a real solution to the power vs. battery-life dilemma. Intel's Speedstep has been a decent stop-gap measure for the last several months, but with PowerNow reaching the market, Speedstep's shortcomings have become painfully obvious. Hopefully Intel's next revision of Speedstep will follow AMD's lead and incorporate some of PowerNow's advantages. Otherwise, Intel's future in the mobile market could be very bleak indeed.
Thanks for reading,
Vic Wang
Computers Advisor - Epinions.com
(Thanks to The Register, Anandtech, AMD Zone, PC Magazine, and X86.org for much of the information contained in this article).
 |
|
|
|
|
|
|
Epinions.com ID:
vicwang
|
|
Member: Vic Wang
Location: Texas
Reviews written: 45
Trusted by: 216 members
About Me:
Systems Analyst and all-around computer guru who's always keeping up with the latest technology.
|
|
|
© 1999-2009 Shopping.com, Inc.