Memtest86 writes patterns to memory and reads them back almost immediately. To do the test properly you need to write a known pattern to memory, wait 24 hours,

Memtest86 writes patterns to memory and reads them back almost immediately. To do the test properly you need to write a known pattern to memory, wait 24 hours, and THEN read it all back and check for flipped bits. If you do not have ECC in your computer, yes you should see some flips.