New
#21
Could find again depending on the motherboard it will reduce the speed to the lowest speed as in 800MHz, I seriously wouldn't bother, 16GB is plenty for most purposes. Generally it's accepted that mixing Ram speeds is not a good idea, if it even works!
That's what I was thinking. OP can look at the sticker on the RAM module and 800 RAM would say PC3 6400 while 1600 would be PC3 12800.
EDIT: Just proved myself wrong. There were 144 pin 800Mhz DDR3 6400 RAM modules made for HP LaserJet printers. https://www.amazon.com/HP-144-pin-DD...language=en_US