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3 AlphaPC 164 Jumper Configuration
The AlphaPC 164 motherboard has three groups of jumpers at location J1, J30, and
J31. These jumpers set the hardware configuration and boot options. Figure 1 shows
the jumper location on the AlphaPC 164 motherboard. Figure 2 shows the jumper
functions for each group. Section 3.1 through Section 3.7 describe the jumper
configurations.
3.1 Memory Bus Width Jumper (J1)
The memory bus width can be either 128 bits (J5 through J8 populated with SIMMs
and J9 through J12 empty) or 256 bits (J5 through J12 populated with SIMMs).
When using a memory bus width of 128 bits, jumper J1 must be in. When using a
memory bus width of 256 bits, jumper J1 must be out.
3.2 System Clock Divisor Jumpers (IRQ3 Through IRQ0)
The system clock divisor jumpers are located at J30–1/2 (IRQ3), J30–3/4 (IRQ2),
J30–5/6 (IRQ1), and J30–7/8 (IRQ0). The jumper configuration set in IRQ3 through
IRQ0 determines the frequency of the microprocessor's system clock output. These
four jumpers set the speed at power-up as listed in Figure 2. The microprocessor
frequency divided by the ratio determines the system clock frequency.
3.3 Bcache Size Jumpers (CF1 and CF2)
The Bcache size jumpers are located at J30–11/12, CF1 and J30–13/14, CF2. These
jumpers configure the Bcache as specified in Figure 2.
3.4 Bcache Speed Jumpers (CF4 and CF5)
The Bcache speed jumpers are located at J30–17/18, CF4 and J30–19/20, CF5.
These jumpers select the Bcache timing parameters used to compute a value that is
loaded into the microprocessor's Bcache configuration register at power-up time.
Because the Bcache SRAMs are soldered onto the board, the default jumper
configuration selecting an SRAM access time of 9 ns as shown in Figure 2 will
always be used.
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AlphaPC 164 Jumper Configuration
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