How many ALUs (and threads) are in a Pentium CPU?
The Pentium processor has two execution units: the U and the V pipes.
  When two instructions execute in parallel in the two pipes, the two
  instructions are considered to have paired.
  
  The U-pipe can execute any instruction in the Intel(R) architecture
  while the V-pipe can execute only simple instructions.
  
  When two instructions pair, the instruction issued to the V-pipe is
  always the next sequential instruction after the one issued to the
  U-pipe.
  
  Simple instructions are entirely hardwired; they do not require any
  microcode control and, in general, execute in one clock. The
  exceptions are the ALU mem, reg and ALU reg, mem instructions which
  are three and two clock operations respectively. Sequencing hardware
  is used to allow them to function as simple instructions.  


Source: http://www.nacad.ufrj.br/online/intel/vtune/users_guide/mergedProjects/analyzer_ec/mergedProjects/reference_olh/pentium4_hh/lips/v_pipe.htm


Source: https://www.ques10.com/p/13341/explain-in-brief-pipeline-stages-on-pentium-proc-1/

So in answer to your question, one ALU can work while the other one is working, so it's not exactly multithreading, because if a thread need u-pipe and it's busy, it will have to wait.