Epson Endeavor - Manual (Page 51)

Note
If the microprocessor in your system is a PQFP type, it is
surface-mounted on the main system board. This means that
if you install an OverDrive processor, you can install it in the
empty OverDrive socket. In this case, you need to disable the
original microprocessor by moving jumper J23 to position
2-3. You also need to make sure the jumper settings for Jl0,
Jll, and J12 are set correctly.
Processor speed jumper settings
You need to change the processor speed jumper settings only if
you replace a 25 MHz processor with a 33 MHz processor.
2-8 Installing and Removing Options