So this is really strange news, reports are going around that there are AMD Ryzen 5 1600 and Ryzen 5 1600X in the wild that have eight working cores. We're not talking about any mods here, there are multiple online reports from users who claim they build a new system and discovered after booting into Windows that they had eight cores and sixteen threads.
WCCF Tech reports the known cases of Ryzen 5 1600 series CPUs with eight cores all seem to belong to a lot that was manufactured in week 36 of 2017 in Malaysia.
Why these processors have more activated cores than they should have remains a mystery. WCCF Tech speculates it could be because AMD is repurposing inventory of its less-frequently sold Ryzen 7 series to meet the higher demand for Ryzen 5 1600 series chips:
Each CPU is tested right before it’s packaged to be shipped, so it’s implausible for the manufacturing facility not to have known that those 1600s and 1600Xs they were shipping weren’t 1800Xs. It’s possible that this was a decision made simply as the result of higher demand on Ryzen 5 1600X and 1600 CPUs leading AMD to use some of its less purchased 8-core dies as Ryzen 5 1600Xs and 1600s to meet the demand.