AOpen AP43 User Manual page 27

Hardware Setup
3.45V CPU Type
INTELDX4 CPUs
You must be able to determine your IntelDX4 CPU type before you set
the jumpers. Improper setting may result to system malfunction.
There are two types of 3.45V IntelDX4 CPUs: one with write-through
mode support while the other is with write-back mode support. To
determine an IntelDX4 CPU with write-back internal mode, look for
the letter "W" in the third row on the lower label of the CPU. The letter
"W" indicates write-back mode. An IntelDX4 CPU with write-through
internal mode does not have this indication. See the following figure.
User's Guide
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