The paper presents a way to speed-up simulation of complex MPSoCs at the TLM/T (transaction level modeling with time) level and a way to switch from abstraction level "at run time". The hardware part of the platform is described in standard SystemC. Rather than using statistical models for adding timing, to obtain an accurate view of the platform dynamic contention is taken into account. This allows to reach a speed-up of up to 50 versus a corresponding BCA simulation with a low timing error. The state saving method gives the ability to save the state of a platform at the TLM/T level and move it to the same platform described at the BCA level. This allows fast and accurate debugging of the embedded software.