[Àû¿ë´ë»ó: 0.74_SVN_new, DOSBox-x]

PCI bus frequency.

WARNING: In future revisions, PCI/motherboard chipset emulation will allow the guest OS/program to alter this value at runtime.

std33.3 : 33.333MHz (very common setting on
             motherboards)
std30 : 30MHz (some older mid-1990's
          Pentium systems)
std25 : 25MHz
<integer or float>:
           Any integer or floating point value will
           be used as the clock frequency in Hz
<integer/integer ratio>: If a ratio is given
           (num/den), the ratio will be used as
           the clock frequency