We have recently manufactured two batches of our custom board featuring the TK1.
One has the MT41K256M16HA-107 IT:E which works well and passes memory shmoo.
The other batch has the MT41K256M16HA-107:E which does not seem to work with the same BCT parameters… nor does it pass the sanity memory shmoo at any frequency.
Is it possible that the difference stems from the different temperature rating? As far as we can tell both chips should have the same timing characteristics (at least at room temperature).