Parrallels Extreme Benchmarking//Performance issue

Hey Guys,
i am running benchmarking and performance check with parrallels extreme version: 4.0.6740(Revision 589767)

HOST Machine
HP z600
12 gb RAM
2 X Quadro FX 1800
Windows 7 64 pro

VM set-up
12 cores
6244MB
Quadro FX 1800 VT-D
Windows 7 64 pro

Test Case Description
3ds max 2011 extension #1
Benchmark Iray, GPU/Cpu based Rendering

HOST run test in same time than VM :

Case #1
HOST run time in: 201 sec
VM run time in: 738 sec
======================
Case #2
HOST do nothing
VM run time about : 260 sec

Is that to be expected ?
My understanding was that VM / host split and reserve resource specifically and then can run heavy application at once without affecting the performance of the other is it the case…?

Is there a way to prevent that Host resource need invasion to affect VM ?
Is there anything I should in the configuration or in the bios that I may need to set-up
To address this ?


thanks