IBM SBC-659P Manuel D’Utilisation

If an insufficient number of cycles is allowed for the RAS to accumulate
its charge before DRAM refresh, the refresh may be incomplete and the
DRAM may fail to retain date. Fast gives faster performance; slow gives
more stable performance.  This field applies only when synchronous

DRAM is installed in the system.

Selecting Enabled allows caching of the system BIOS ROM at F0000h-
FFFFFh, resulting in better system performance.  However, if any program
writes to this memory area, a system error may result.  The choices:

Selecting Enabled allows caching of the video BIOS ROM at C0000h to
C7FFFh, resulting in better video performance.  However, if any program
writes to this memory area, a system error may result.  The choices:
Enabled, Disabled Memory

In order to improve performance, certain space in memory is reserved for
ISA cards.  This memory must be mapped into the memory.  The choices:

During enable, a deferrable CPU cycle will only be Deferred after it has
been in Snoop Stall for 31 clocks and another ADS# has arrived.  During
disable, a deferrable CPU cycle will be deferred immediately after the

GMCH receives another ADS#.

The chipset has an embedded 32-bit posted write buffer to support delay
transactions cycles.  Select Enabled to support compliance with PCI
specification version 2.1.