Intel Core 2 Duo E8800 (ES)
Intel Core 2 Duo E6200 (ES)
Intel Core 2 Duo E7700
Intel Pentium II 266 (0,35µ)
Intel Core 2 Duo E7800
Means Super Low Frequency Mode.
It is a functionnal mode where a cpu featuring Intel Enhanced Speedstep Technology (EIST) work at FSB frequency (coeff = 1.0x).
Knowing that FSB cannot be modified dynamically by a cpu itself, it is the slowest operating frequency of cpu today.