Every time that Apple updated their OS, it required more RAM and a faster processor. Then came Mac OS X. Version 10.0 ran slowly on anything.
OS X 10.1 was a big improvement over that, including many features (such as CD burning and the ability to play DVDs) that were missing from 10.0.
When Apple started marketing OS X by codename, Jaguar (10.2) was another step up in terms of performance. It lived up to its promises - on the 15" PowerBook G4/400 I had at the time, it ran significantly faster than 10.1 had - and that was with just the basic 128 MB of RAM that came with the machine. Of course, it ran much better on my 12" PowerBook G4/867 with 256 MB of RAM.
Then came 10.3 (Panther). It ran decently on the 12" PowerBook G4, but with only 256 MB of RAM, some applications would struggle. When I upgraded from Office v. X to Office 2004, I noticed a significant performance drop. While Office 2004 had some great features that (these days) I'd struggle to live without, it certainly seemed to like using up my RAM.
While OS X doesn't give "out of memory" errors like the classic Mac OS used to, you can tell when it's out of physical memory by the performance - or lack thereof.
I held off on Tiger (OS X 10.4) for a while. Panther's a great operating system, and all of the software that I use runs just fine on it. However, the convenience of the dashboard on my Power Mac G5 (see Moving Up from a 15" 350 MHz Power Mac G3 to a Dual 1.8 GHz Power Mac G5 for that story) got to me, so I decided it was time to upgrade my PowerBook as well.
It really wasn't a big deal. Installing Tiger was like installing any other version of OS X, and pretty soon the machine was up and running again. I eagerly clicked on the dashboard - and waited - and waited - while the hard drive made all sorts of noise. Finally the default widgets jerked into view on the screen.
I added a couple others, and waited for them to be updated online. I must've waited about 5 minutes, and nothing had happened! I clicked the dashboard off and on a few times . . . and finally one at a time they started updating themselves with the current weather and time.
Tiger might as well have been called "Tortoise" on this PowerBook. Doing anything - even opening iTunes - was painfully slow. Firefox would run out of RAM and crash several times in an hour. iPhoto would start failing whenever I asked it to do a slideshow.
It was beyond ridiculous, it was unusable. 10.4 seemed to mark the end of OS X getting faster with each revision. Sure, Tiger might be faster - but only on the newest hardware.
I then figured that while 256 MB had been adequate for previous versions of OS X, even the Mac mini comes with 512 MB these days. There's no reason why my PowerBook shouldn't have at least that much, so I picked up a 512 MB upgrade and installed it, bringing total RAM to 640 MB (128 MB is built-in).
The performance increase was dramatic. For the first time in the two years that I've had this machine, it's actually been quick - faster than it ever was with 10.2 or 10.3.
Okay, it doesn't boot up as fast as the G5, but Firefox launches quickly, iTunes doesn't give me any more trouble, QuickTime and Windows Media videos play without a problem, and the dashboard even works as it's supposed to (though it seems the ripple effect doesn't work on G4s). I installed iPhoto 5, and it's currently updating my photo library as I type this and listen to music in iTunes.
Just as a quick test I typed a search in Spotlight. I was curious to see how quickly the machine would find the original file for "The Accolade" by Symphony X. It took about 3 seconds.
The fact that it seems to be able to perform basic tasks quickly and efficiently shows me that it's not so much the OS by itself, but the additional applications that slow the machine down. If I were still running the exact same applications as I had been two years ago when I bought the machine (and there are a few I still use), I would probably have very few problems with performance. For a PowerBook, 867 MHz shouldn't be a speed slouch - and it's not with a decent amount of RAM.
Is Tiger actually faster than Panther and Jaguar, or is this the end of OS X getting faster with every new version?
Since I've never run Jaguar or Panther on this machine while it had 640 MB of RAM installed, I'll never know for sure.