Intel Celeron 366
Pentium II Xeon 450
I have three Celeron 366's:
1. This one with sSpec SL35S that was a Boxed CPU without heatsink.
2. The SL36C which is identical but for OEM's (came in trays).
3. A Slot 1 variant. It also has an A-stepping core.
Basically they all work identical. The Slot 1 CPU I have is a bit older and uses the A0-stepping core instead of B0-stepping.
Performance-wise the Celeron 366 is about identical to the Pentium II 350. The Celeron was usually favorable due it's price point and, for enthusiasts, it's overclock ability.
