Jp38, Jp42: Bus Fraction Core/Bus Ratio Select - SOYO Pentium SiS 551x User's Manual & Technical Reference

Hardware Setup
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JP38, JP42: Bus Fraction Core/Bus Ratio Select

Set this jumper according to your CPU clock and this setting is only for Pentium.
Note: For PentiumX /Y MHz, X stands for CPU core clock, Y stands for bus clock.