CR0_CD
lcr0((rcr0() & ~CR0_NW) | CR0_CD);
lcr0(rcr0() & ~(CR0_CD | CR0_NW));
if ((r & CR0_NW) && (r & CR0_CD) == 0) {
{ CR0_CD, "CD ", "cd " },
lcr0((rcr0() & ~CR0_NW) | CR0_CD);
lcr0(rcr0() & ~(CR0_CD | CR0_NW));