Graphics Controller
Overview
The VAXstation 4000 Model 90 workstation supports three
graphics options: LCSPX, SPXg, and SPXgt. The LCSPX module
is a low cost graphics module, while the SPXg/gt modules support
high performance 3D graphics. The SPXg is an 8-plane graphics
module and the SPXgt is a 24-plane graphics module. Note
that only one video option can be physically installed into the
workstation at a time. All the graphics options share a single
interrupt request signal and interrupt vector. The graphics
interrupt can be enabled/disabled by a bit in the INT_MSK
register. All of the graphics options can be reset with the graphics
reset bit in the IORESET register. Two bits in the configuration
register allow software to determine if an LCSPX or a SPXg/gt
module is installed in the system.
LCSPX
The LCSPX module is a redesign of the VXT 2000 SPX module.
This is a cost-reduced SPX module that interfaces directly to the
CP2 bus. The LCSPX module is functionally the same as the VXT
2000 SPX module except that two video oscillators are supported
using a module switch. The diagnostic ROM/Configuration
register on the LCSPX module contains information about
the oscillator currently in use. This is the only register that is
different from the VXT 2000 SPX module. Table 1–6 shows the
bit definitions associated with the diagnostic ROM configuration
register.
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