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
R O M 3
b y t e 3
b y t e 7
b y t e B
R O M 2
b y t e 2
b y t e 6
b y t e A
R O M 1
b y t e 1
b y t e 5
b y t e 9
R O M 0
b y t e 0
b y t e 4
b y t e 8
2 0 0 4 . 0 0 0 0
2 0 0 4 . 0 0 0 4
2 0 0 4 . 0 0 0 8
L J - 0 1 8 1 8 - T I 0
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.
Continued on next page
2–11
