Specifications

2–6 System Configuration and Connectors
Subject to Change – 17 January 1997
AlphaPC 164 Jumper Configurations
2.1.2 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 2–2. The
microprocessor frequency divided by the ratio determines the system clock
frequency.
2.1.3 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 2–2.
2.1.4 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 2–2 will
always be used.
2.1.5 Mini-Debugger Jumper (CF6)
The Mini-Debugger jumper is located at J30—21/22 (CF6). The default position for
this jumper is out (Figure 2–2). The Alpha SROM Mini-Debugger is stored in the
SROM. When this jumper is in it causes the SROM initialization to trap to the Mini-
Debugger (communication through connector J32) after all initialization is complete,
but before starting the execution of the system flash ROM code.
2.1.6 Boot Option Jumper (CF7)
The boot option jumper is located at J30—23/24 (CF7). The default position for this
jumper is out (Figure 2–2). This jumper selects the image to be loaded into memory
from the system flash ROM. With the jumper out, the Windows NT ARC firmware
is loaded. With the jumper in, the fail-safe booter is loaded. For more information
about the fail-safe booter, refer to the AlphaPC 164 Motherboard User’s Manual.