Im running Cubase SX 1.06, AL powerbook 15in 512mb ram, stock sound, oxygen8 controller.

When using no more than Kontakt (3 sample sets), absynth and the AB-1 synth in cubase, I get VST performance spikes which causes cubase to crackle and carry on.

Should I be able to run more than this? like when it doesnt spike, vst performance sits at about 40% mark then just spikes heaps and crackles. What are the buffer settings I should be running in SX? Are there any other setting that would help this? Would a better soundcard fix this? any help would be great, im kinda new to macs.

You probably should be able to run more than that. More RAM would help, but the problem might be your sound I/O (what is it - FireWire, USB, stock ports?), the hard disk (ie not using an external FireWire drive), SX itself or simply the amount of activity happening at any one time.

If there's too much going on at a particular point in the song, that can cause the system to "choke". Have you tried the cubase.net forums for more specific help? I had similar problems with SX, but now use Logic so I've hopefully left them behind.

Give us a bit more info and we might be able to help some more.

I had similar performance probs running SL on a G4/500 Pismo, OS 10.2.8, and found a big improvement after implementing the following tips for optimizing the system for music apps here:

http://forum.cubase.net/forum/Forum1/HTML/015428.html

Hope this helps you too.

just the stock sound card. im not too sure why it could be, could it be because some of the samples in the kontakt sample sets 24bit? if I got a profesh type audio card (was thinking the motu 828) would something like that be likely to take some of the load off?

vst settings are as
disk buffer size ; 256kb
number of disk buffers ; 4
audio buffer set to 768kb (bit laggy at that setting but bareable)
the rest is left stock.