NEC POWERMATE PROFESSIONAL - SERVICE MANUAL 05-1997 Service Manual page 63

ISA LFB Size
The ISA Video Linear Frame Buffer (LFB) Size provides a mechanism for creating a hole in
the system memory map. Address accesses made to this hole will be directed to the ISA bus
instead of main memory.
This "Disabled" setting should not be changed unless you are using an ISA board that has
memory greater than 64K, needs to be accessed by the CPU, and you are not using the Plug
and Play run-time utilities. The following choices are available:
T
Disabled (default)
T
1 MB.
ISA LFB Base Address
This field cannot be entered; it is an information field only. If the ISA LFB field is
"Disabled," this field does not appear.
The ISA Video LFB Base Address field displays "15 MB" (the starting address of the ISA
memory hole) if "1 MB" is chosen as the ISA LFB Size parameter.
Video Palette Snoop
The Video Palette Snoop field enables card "snoop" (also called RAMDAC shadowing)
write cycles to the ISA video card's palette registers. This field can be either "Enabled" or
"Disabled;" the default is "Disabled."
This should only be set to "Enabled" if all of the following conditions occur.
T
An ISA card connects to a PCI Graphics card via the VESA-compatible feature
connector.
T
The ISA card connects to a color monitor.
T
The card uses the RAMDAC on the PCI card.
T
The palette snooping feature is broken on the PCI card.
Latency Timer (PCI Clock)
The Latency Timer (PCI CLOCK) field controls the length of time an agent on the PCI bus
can hold the bus when another agent has requested the bus. Value choices range between 0
and 256; the default value is 66.
In general this should not be changed. If there are latency-sensitive cards in the system
(such as audio cards and/or network cards with small buffers), this can be set to a lower
value to reduce latency.
Setup and Operation 2-21