Chapter 3
27
AGP Secondary Lat Timer
This BIOS feature controls how long the AGP bus can hold the PCI bus (
via the
PCI-to-PCI bridge
) before another PCI device takes over. The longer the latency, the
longer the AGP bus can retain control of the PCI bus before handing it over to another
PCI device.
Normally, the AGP Secondary Latency Timer is set to
20h
(
32 clock cycles
). This
means the AGP bus' PCI-to-PCI bridge has to complete its transactions within 32
clock cycles or hand it over to the next PCI device.
For better AGP performance, a longer latency should be used. Try increasing it to
40h
(
64 cycles
) or even
80h
(
128 cycles
). The optimal value for every system is different.
You should benchmark your AGP card's performance after each change to determine
the optimal latency for your system.
If you set the AGP Secondary Latency Timer to a very large value like
80h
(
128
cycles
) or
C0h
(
192 cycles
), it is recommended that you set the
PCI Latency Time
to
32 cycles
. This provides better access for your PCI devices that might be
unnecessarily stalled if both the AGP and PCI buses have very long latencies.
In addition, some time-critical PCI devices may not agree with a long AGP latency.
Such devices require priority access to the PCI bus which may not be possible if the
PCI bus is held up by the AGP bus for a long period. In such cases, it is recommended
that you keep to the default latency of
20h
(
32 clock cycles
).
HyperTransport Config
Hammer to M1689 Freq.
This feature allows you to select the M1689 Hyper transport frequency.
Hammer to M1689 Width
This feature allows users to select the M1689 Hyper transport width.
M1689 HTT TriState
If enabled, the HTT transmitter tristates the link during the disconnected state.
Memory Hole At 15M-16M
This feature enables users to determine whether the 15
th
~16
th
(1MB) block of memory
will be reserved for the ISA cards or not. If
enabled
, 1MB of memory will be
reserved exclusively for the ISA cards. Thus the total amount of memory the
operating system uses will decrease. If
disabled
, the 15
th
MB of RAM will not be
reserved for the ISA cards and there will be a full range of memory available to the
operating system. Since the ISA cards are a thing of the past, it is highly
recommended that you
disable
this feature.
Содержание ULi M1689
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