I have tested these CPUs in a DFB1X at 50MHz. See the Info link for tests I do. They have been tested without heatsink and deemed to work fine. Though I do not recommend running without a heatsink for extended periods of time.

These are not sourced from China and are genuine NOS ! Picture is for illustration only.

I also sell small stick-on heatsinks item #0222, or larger ones item #0280