HP Vectra Reference Manual page 99

Jumper W2 must be installed on pins 1 and 2 of P4 for operation
with a 15 kHz monitor. Jumper W2 must be installed on pins 2
and 3 of P4 for operation with a 25 kHz monitor. The following
figure shows the configurations for this jumper.
W2 Configurations
P2
SETTINGS
=60 Hz
=50 Hz
Figure 20
P4
SETTINGS
=
25
kHz
=
15 kHz
Table 7.1 defines the pin assignments for the hardware interface.
The signal definitions for these pins are defined in Section 2.
Tables 7.2 through 7.4 defines the pin assignments and signal
definitions for peripheral devices.
82 Multi-Mode Video Adapter Card