def get_series(boot_hart, bitness):
    """Given the boot hart and the bitness, get the SiFive core series name"""
    hart_compat = boot_hart.get_field("compatible")
    series = None
    if "bullet" in hart_compat:
        series = "sifive-7-series"
    elif "caboose" in hart_compat:
        series = "sifive-2-series"
    elif "rocket" in hart_compat:
        series = "sifive-3-series" if bitness == 32 else "sifive-5-series"
    return series