How to avoid 4 core limit for Ubuntu within VMWare?

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http://unix.stackexchange.com – I have Ubuntu installed as VM on my laptop. My laptop has quad core with HT technology making it 8 cores. Within Ubuntu VM I can only use max of 4 cores. What should I do so I can access all 8? Which Linux distribution would let me use all my cores? Which VM software should I use? Any advices? (HowTos)