Compact implementation of logical AND in x86 assembly -

hi, x86 assembler geeks!

i have interesting problem test assembler programming skills.
i'm author of problem, know correct answer.

your task implement logical and in x86 assembly , satisfy following 5 conditions:

condition #1
boolean values encoded in 16-bit words in standard way:

0x0000         = false 0x0001..0xffff = true 

condition #2
operation "logical and" 16-bit values looks following:

  logical_and(value1,value2) == 0    if (value1 == 0) or (value2 == 0)   logical_and(value1,value2) != 0    if (value1 != 0) , (value2 != 0) 

you must give correct result 16-bit value1 , value2.
please note free choose nonzero value "true" result, not 0x0001 or 0xffff.
example, allowed have logical_and(0xdead,0xbeef) == 42

condition #3
should write 16-bit code x86 real mode.
input parameters in ax , bx, result in ax:

  ; registers on entry:   ;  ax = value1   ;  bx = value2   (your code goes here)   ; registers on exit:   ;  ax = logical_and(value1,value2)   ;  bx,cx,dx,si,di,bp , 32-bit extensions may contain garbage on exit 

obviously, single instruction and ax,bx not enough: when ax=1 , bx=2, result must nonzero.

condition #4
x86 instructions allowed (even sse).
can use stack.
neither external code (call externalproc, int xx) nor external lookup tables permitted.
initialized data should inside chunk of code.

example solution (12 bytes of code)

   ; **** entry: ax, bx    test ax,ax    setnz al    test bx,bx    setnz bl    , ax,bx    ; **** exit: ax 

example solution (6 bytes of code)

   ; **** entry: ax, bx    neg ax    sbb ax,ax    , ax,bx    ; **** exit: ax 

example solution (5 bytes of code)

   ; **** entry: ax, bx    cmp ax,bx    jb @done    xchg ax,bx @done:    ; **** exit: ax 

condition #5
you must perform task using 4 bytes of code.

probably, have found short solution input parameters in ax , cx.
nice try!
unfortunately, solution not correct answer (because of using cx input).

probably, there more 1 correct answer exist.
anyway, first correct answer (which satisfies 5 requirements) awarded 500 rep points bounty.

my own 4-byte-long code quite unexpected , has remarkable property.

please not brute-force. use brains.

to moderators:
not code-golf. first correct answer accepted.

 mul bx   or  ax, dx 

on older machines might not fast compared longer answers.