; RDRAND · HW free RNG · AMD 7900X has it · never eaten into SDF
; LINEAR BGS->BGF->SDF · atoms EZZIE PHI THERMO on BGF · free rides · no duo
; out: eax = random |1 · CF=1 success path assumed
; retry light · linear · no fold
        rdrand  eax
        jnc     .r
.ok:    or      eax, 1
        ret
.r:     rdrand  eax
        or      eax, 1
        ret