Whether you're using a PC or a Mac (whether Intel, Power PC, oreven 68K), there are four components that affect the speed of yourlaptop - and in some cases they also affect battery life inverselyproportionate to speed.
Want a faster processor? It will suck your battery dry fasterthan the same chip at a slower clock speed.
On a desktop computer, these things are usually played out interms of speed against price, with power being relativelyunimportant. For laptops, however, manufacturers must choosecomponents far more carefully.
The four components are hard drive, memory, processor, andsystem chipset (bus speed). There are other areas where performanceor battery life can be optimized, such as your choice of wirelesscard on PC laptops, but the biggies are the ones I mentioned.
How much difference a given component makes to laptopsperformance compared to how big a hit your battery life takes isthe big struggle in designing the ultimate high-performance,long-running portable. Lets look at each one.
Bus Speed
Bus speed is set by the your computer's chipset, and it's theone thing that buyers have almost no control over except in theused market, where bus speed is chosen by the age of acomputer.
For Apple, look at a Lombard G3PowerBook from 1999 side-by-side with its replacement, thePismo model of the year 2000. Busspeed increased from 66 MHz to 100 MHz while most other componentsremained fairly consistent. A top-of-the-line 400 MHz Lombard and abottom-of-the-line 400 MHz Pismo were fitted with almost identicalprocessors, the Pismo performed considerably better even with thesame clock speed on the processor. Any battery life advantage theLombard may hold was insignificant, meaning that with everythingbeing equal(which it seldom is), bus speed is an area where you cansee real performance improvement without much penalty in batterylife.
This doesn't always work out. When Intel moved from the Dothanto the Sonoma chipset last year, bus speeds rose from 400 MHz to533 MHz, but performance gains were almost nonexistent whilebattery life went way down. I had an IBM ThinkPad T42p at the time,and compared to the T43p with the faster bus speed, the T42preturned almost identical benchmarks in both test programs andframe rates on real games. The T43p, however, ran for 30 minutesless on its 20% higher capacity batteries.
Was it the chipset that sucked more power? I'm really notconvinced, but the fact remains that over on the IBM ThinkPadforums there were a lot of complaints about the T43 series, withmany users ordering new T42s until the supply ran out a few monthsago.
CPU
The next key component is the processor, and again we have aless-than-clear picture of performance versus efficiency. Intel'sCore Duo processor is extremely powerful - more powerful than thePentium M it replaced - and by most accounts thus far Core Duoreturns spectacular battery life.
Looking at ThinkPads again, I currently use an X41 with a 1.6GHz Pentium M of the final Sonoma series. Its replacement, the 1.66GHz ThinkPad X60s, has the Core Duo. Both computers use theso-called "low voltage" versions of their processors, but the newX60s, despite a slightly higher clock speed and considerably morepower, runs significantly longer on its battery.
Stranger still, the X60s has a larger and faster hard drive thatshould use more power, not to mention a faster bus speed. The CoreDuo does run a bit hotter, but it's combination of power andefficiency are far better than its predecessor.
Memory
RAM is a no-brainer. More RAM increases computer performance andat the same time increases battery life. The RAM chip itselfrequires power to store data, but by preventing the need to swapthat data to and from the hard drive, which consumes far more powerthan RAM does, having more RAM actually saves battery power - to apoint.
With Windows XP or Mac OS X and moderate application use, 1-2 GBof RAM provides a fine balance.
Imagine that you could stuff 8 GB of RAM into your portable,however. In that case, you would be supplying power to keep data inthose chips, but since you were only using 1-2 GB of RAM anyway,you would no longer be preventing hard drive swaps, and thus yourbatteries would run down sooner than on a 2 GB machine.
Still, RAM chips use very little power, so more is usuallybetter.
Hard Drives
The final component, and the area where laptop users can givethemselves real performance boosts, is the hard drive. Most laptopsstill come with 4200 rpm hard drives, while Apple has moved theirentire line to 5400 rpm (and even 7200 rpm) drives.
Again we have a compromise. The faster a given drive spins, thefaster its head can read and write data. This is a real performanceboost you will see every time you boot your computer, launch anapplication, or open and save large files.
Conversely, spinning a platter at 5400 rpm uses more power thanspinning it at 4200 rpm. It's a balance, made more complex bycaching schemes, the areal density of the individual driveplatters, and the controller chips on both the computer and thedrive itself.
I like Hitachi TravelStar drives, not because they are betterthan their Toshiba, Fujitsu, Samsung, or Seagate competition, butbecause I've owned many over the years and they've always served mereliably, and, most important, quietly. I'm sure the competition isjust as good, including a Samsung drive in one of my PowerBooksthat gave excellent and silent service.
The key is to compare drives from a single manufacturer in thesame capacity for performance and battery life when looking at theeffects of rpm, and I've made that comparison with Hitachidrives.
Benchmarks
My daughter has a 4-year-old IBM ThinkPad X22, a small laptopwith an 800 MHz Pentium IIIm processor and a 133 MHz system bus. Inshort, it's no speed demon - but not sluggish either. I took a diskimage in Norton Ghost and flashed it onto the three 80 GB harddrives I have: 4200 rpm, 5400 rpm, and 7200 rpm Travelstars thatall have the same 8 MB cache.
Booting Windows XP takes 72 seconds with the 4200 rpm drive frompressing the power button until the hourglass goes away on a fullWindows desktop. With the 5400 rpm drive that figure drops to 65second, with another drop to 54 second with the 7200 rpm drive.
Most people won't care about 18 seconds when starting theircomputer, but consider that booting up a computer is only part diskaccess, there are also memory and system tests going on as well asdozens of other hardware functions.
A better test is a disk copy. I prepared a folder filled withdocuments and files of various sizes ranging from 10 KB to 10 MB,with the total size of the folder at 400 MB, and copied it from onefolder to another on the same drive. The 7200 rpm drive was a full2 minutes faster than 4200 rpm drive, with the 5400 rpm drive inthe middle, though closer to the 4200 rpm drive.
Battery life was similarly affected, though this is an examplewhere the higher performance drive is a good tradeoff for itsbattery life penalty, depending on how you use your computer. TheThinkPad X22's battery is fairly large, though a few years old.When new it ran for over four hours, but these days its good forabout 2.5 hours in casual use.
I tested runtime with the DVD Lawrence of Arabia, knowingthe movie lasts longer than the battery. With the 4200 rpm drivethat is normally in this computer, I was able to run the DVD for 1hour and 44 minutes. With the 5400 rpm drive, it ran for 1 hour and40 minutes, while with the 7200 rpm drive it ran for 1 hour and 33minutes. That's only 11 minutes difference between the fastest tothe slowest drive - and a good argument for running the fasterdrive unless every minute of battery life counts.
Even then, you might find yourself productive instead ofwatching the hourglass or spinning beach ball longer than thebattery increase on the slower drive, making a fast drive the bestimprovement you can make.
More important than rotational speed, however, is areal density.I ran the same tests again with the 20 GB drive that came with theThinkPad, a 4200 rpm drive with a 2 MB cache. Booting Windowstook a full 98 seconds, 26 seconds longer than with the 80 GB 4200rpm drive and its 8 MB cache. Some of that was cache, but mostwas the greater aerial density - how densely packed the data is inthe drive.
Imagine you're trying to pick up cones on the road and have amachine that just grabs them as you drive by. Rotational speed ishow fast you drive by picking up cones, whereas aerial density ishow close the cones are to each other. At 10 MPH you will pick upcones twice as quickly if they are 4 meters apart than if they are8 meters apart, just as you will pick up twice as many cones at 20MPH as at 10 MPH.
Comparing the 20 GB and 80 GB 4200 rpm drives, the 20 GB drivehas a pair of 10 GB platters whereas the 80 GB drive has a pair of40 GB platters. The platters are the exact same size, only theyhold 4x as much data, meaning the "cones" are four times as closetogether.
The Best Upgrade
So what's my point? Simple: Put as much RAM into your laptop asit or your budget will allow, although there's little reason formost users to go past 2 GB with Windows XP or Mac OS X,and strongly consider upgrading to a modern, fast hard drive.
Even if you have a fast 5400 rpm drive in your machine, if thatdrive is only a 20 GB or 40 GB model, you'll see a real performanceincrease moving to an 80 GB or larger drive even if the rotationalspeed is lower. Grab yourself a large drive with a fast rotationalspeed, and you'll be rewarded with greatly increasedperformance.
Modern drives are more power-efficient as well. In my DVD test,the old 20 GB drive was only able to run for an hour and 28minutes. That's five minutes less than the fast 7200 rpmdrive. 
Andrew J Fishkin, Esq, is a laptop using attorney in Los Angeles, CA.
