PR_SID
int mid = mfpr(PR_SID);
mid = mfpr(PR_SID);
vax_cputype = (mfpr(PR_SID) >> 24) & 0xFF;
vax_cpudata = mfpr(PR_SID);
mfpr(PR_SID) & 65535, (mfpr(PR_SID) >> 16) & 127);