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AlphaPC 164LX Jumper Configuration
The AlphaPC 164LX motherboard has two groups of jumpers located at J27 and J28,
as shown in Figure 2–1. These jumpers set the hardware configuration and boot
options. Figure 3–1 shows these jumper configurations.
3.1 CPU Speed Selection
The clock synthesizer at location U47 makes it possible to change the frequency of
the microprocessor's system clock output without having to change the clock crystal.
Simply set the system clock divisor jumpers to adjust the frequency of the
microprocessor's system clock output. These system clock divisor jumpers are
located at J27–1/2 (IRQ3), J27–3/4 (IRQ2), J27–5/6 (IRQ1), and J27–7/8 (IRQ0).
The jumper configuration is set in IRQ3 through IRQ0. These four jumpers set the
speed at power-up as listed in Figure 3–1. The microprocessor frequency divided by
the ratio determines the system clock frequency.
3.2 Bcache Size Jumpers (CF1 and CF2)
The Bcache size jumpers are located at J27–11/12 (CF) and J27–13/14 (CF2). These
jumpers configure the Bcache as specified in Figure 3–1.
AlphaPC 164LX Jumper Configuration
3
3–1
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