Technical data

System ROM
Overview
The base VAXstation 4000 Model 90 firmware contains 512 KB of
ROM split into four 128-KB wide ROMs. This provides the full
32-bit wide memory data path shown in Figure 2–1.
Figure 2–1 System ROM Format
ROM 3
byte 3
byte 7
byte B
ROM 2
byte 2
byte 6
byte A
ROM 1
byte 1
byte 5
byte 9
ROM 0
byte 0
byte 4
byte 8
2004.0000
2004.0004
2004.0008
LJ-01818-TI0
The system firmware ROMs supply some information on a per
byte basis for ease of manufacture and development. Other
information (software and tables) is supplied by the set of ROM
parts. Figure 2–2 displays the system ROM part formats.
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