Logic Pro 9 Logic 9.1.3. CPU spikes problem


New Member
Hey there

Just wondering if anyone can help.

I'm getting CPU spikes on logic sessions [i.e. from 1 or 2 bars on the CPU meter, to near full bars in a quick jump and then down to 1 or 2 bars again].
The HDD bar goes in sync from 1 bar to say 4 or 5 bars.

Often it also spikes to the maximum and then playback stops with an error saying not enough processing [-10011]

I'm only playing back 20 audio track with no plugins on them, and recording in on 6 stereo tracks [24 bit 44.1K]. If I stop the recording of the stereo tracks and just play the recorded signal with the other tracks the problem still occurs

The buffer size selected doesn't make a difference to this spiking (or how much it raises) whether it is at 64 samples or 1024 samples.
Process buffer was set at medium or large
Logic is using ~1.9 Gig of memory
Tried in 32 and 64 bit mode, no difference

Computer specs
Hardware Overview:

Model Name: Mac Pro
Model Identifier: MacPro1,1
Processor Name: Dual-Core Intel Xeon
Processor Speed: 2.66 GHz
Number Of Processors: 2
Total Number Of Cores: 4
L2 Cache (per processor): 4 MB
Memory: 9 GB
Bus Speed: 1.33 GHz
Boot ROM Version: MP11.005C.B08
SMC Version (system): 1.7f10

Hard drives - ran off internal 7200 SATA drive and Firewire 800 and no difference to the CPU spiking problem [i.e. the same]

Any help much appreciated