Monday, March 11, 2013

Playing around with ArchC: TLM and multicores

As the final goal of my MSc thesis is to create a simulation framework for the SHMAC (Single ISA Heterogeneous Multicore Architecture Computer) I've been spending some time on creating ArchC/SystemC simulations for multicores and interconnects, and it feels like I'm finally getting to a point where I have a clearer picture of the concepts involved. Or so I hope :)

A bit of a background on SHMAC: it's a tile-based heterogeneous architecture which was first realized on an FPGA last year in the form of this MSc thesis by Leif Tore Rusten and Gunnar Inge Sortland at NTNU. The simulator I'm developing will (hopefully) eventually be used to evaluate interconnect and cache matters for the architecture.

It's mostly the "Processor Design with ArchC" chapter of the "Processor Description Languages" book that motivated me to write this - it gives a little warm-up on the features of ArchC including the TLM memory and interrupt controller port, and then goes on to how these concepts could be used to construct a two-core system.

// ...includes, includes...
int sc_main(int ac, char *av[])
{
    mips1 proc1("p1");
    mips1 proc2("p2");

    someBus bus("b");
    someMemory mem("m");

    proc1.memoryPort(bus);
    proc2.memoryPort(bus);
    bus.memoryPort(mem);

    // ...even more connections, omitted since they're related to the interrupt controller
    proc1.initAndLoad(someBinary);
    proc2.initAndLoad(someBinary);

    sc_start();

    // ..print start and exit
}


Despite how promising it looks, there unfortunately is no source code that follows with the book (at least that I'm aware of) - even though it is rather well described how the top-level components are connected in the code example in the book, how the memory, bus and interrupt controller are actually implemented is not mentioned. And I was unable to find any further code examples using ArchC for multi-core simulation. So I decided to take the plunge into ArchC's documentation and source code to understand how I could make it work, and well, I guess I can say the results are better than expected :)

More implementation details and juicy TLM stuff (not really, it's actually quite simple) coming up in the next post!

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