[brianolson]

Yield. Some fraction of cores had a speck of dust or something, but at 38/40 good cores per chip they got economical yield

[tjhei]

And then even if some nodes had 40/40 "good" cores, it would make load balancing a lot more complicated if core counts vary. Easier to turn them off at the hardware level.

[dist-epoch]

Couldn't some chips have 40 good cores, while others have only 36? Do they all need to be exactly 38?