Another KDE4/Akonadi/Stringi/Neopunk Thread (okay, mostly KDE4...)
 

I don't really have a dog in the fight. This is mostly observational and piques my curiosity. Two roughly comparable systems with different behaviors:

1. My wife's e-Machines desktop:

• AMD Sempron ~1.8 GHz
• 2 GB RAM
• nVidia GeForce using propriatory (sp?) driver
• Stock Slackware64-13.37
• Runlevel 4 w/ 2 X sessions: 1 KDE + 1 XFCE or Fluxbox

2. My new (to me) Lenovo T60 laptop:

• Intel core duo 1.6 GHz
• 2 GB RAM
• ATI Radeon using open radeon driver
• Slackware64-current w/ Alien's KDE 4.7
• Runlevel 3 w/ single X session KDE (or XFCE or fluxbox)

Seems like both should be modern enough to run KDE4, but it is slightly laggy on the laptop. I didn't really notice until I fired up kbreakout on the laptop and had serious refresh problems. I quit X and restarted using XFCE, and performance was fine. Never had this problem on the desktop, even running two desktops with several Firefox tabs each! ;).

Do you think this is a video issue? I haven't disabled any KDE bells or whistles.

Another bit of info is that the laptop USB controller is non-functional. (Got it cheap! :D) Could some KDE component be choking trying to poll USB devices?

Will try some other tests and tweaks. Meanwhile any other ideas?

To narrow it down.
While in Kde I'd check for cpu and disk activity. If there is more activity than there should be then some software component is running wild and slowing down the system.
If cpu and disk activity is normal, then it's the video driver.
In that case get an accelerated video driver if you can find one that's good enough.
Unfortunately I don't know much about the ATI drivers as I make it a point to avoid hardware with ATI chips and stick to Nvidia based video hardware.
If your laptop has one of those "express" slots (or whatever they're called) you could get a card with usb ports and gain usb functionality again.

Yeah, I do plan to look into some of this. I didn't notice any increase in audible fan or disk activity. I've just been using fluxbox lately anyway. Games and videos are working fine, so sorting this out is not a huge priority.

Yep, that's been my plan!

My desktop (which sounds quite like your wife's desktop) started showing slow graphics behaviour (like you noticed with a trivial game - kpatience). I have conky running in a corner of all my desktops and noticed that kded was running 90% of the cpu. If you started a lot of other programmes it happily ceded cycles to them, but as soon as they were stopped, kded upped its cpu and memory needs. Log out of KDE back to command line. Restart KDE. kded still doing the same. Google for the problem - others have said that you need to kill kded explicitly and restart. This worked and the PC is back to normal running without obvious graphics sluggishness.