MSI MS-5148 User Manual page 52

Memory Hole At 15M-16M
Choosing Enabled will enable a memory hole in the DRAM space.
The CPU cycle matching the enabled hole will be passed on to the PCI. PCI
cycles matching an enabled hole are ignored. Disabled (default) will disable
this function.
Note: A selected (Enabled) hole is not remapped.
PCI 2.1 Compliance
The Settings are Enable or Disable. During Enable those PCI Soft
with PCI 2.1 compliance will perform better, but some PCI card does not meet
PCI 2.1 compliance. The default setting is Disabled.
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