At .75v 193mhz i get all x on first two rows of both chips at 193mhz
If i set a high timeout i get better ghs but xs still come just not as fast. Around 30-75ghs

How are you optimizing units some read .74 to .75 should they be more stable maybe remove some lead...

Mine is a jan or feb 2014 antminer s1 on the stamp on pcb are these different

I really want an extreme undervolt it was so stable overclocked. Should I go up to .8v

Also off topic i notice my fan on corsair 500 bronze doesnt spin anymore on the s1 since undervolting.  Is it because watts are so low or should I try another psu.  I believe I had same results on my gold psu with x's but fan spun on that psu.