IBM Aptiva 2142 - Manual (Page 152)

Pentium MMX Processor Speed—Type A-1
The Processor speed jumpers are set to the manufacture Type and Model of
the Aptiva computer. Changing jumper settings are not supported and might
cause system failures.
Figure 5-2. Pentium MMX Processor Speed—Type A-1
Pentium MMX Jumper 166
MHz
200
MHz
233
MHz
Processor Speed MHz JP3
JP12
1-3, 2-4
1-2, 3-4 3-5, 2-4
1-2, 3-4 3-5, 4-6
1-2, 3-4
5-4