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Motherboard BIOS and Setup Utility
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3.14.10.3 ISA Shared Memory Size
Sets a range of memory addresses that will be directed to the ISA bus rather than on-board
memory. The options are:
• • Disabled (default)
• 16 KB
• 32 KB
• 48 KB
• 64 KB
• 80 KB
• 96 KB
If this is set to Disabled, the ISA Shared Memory Base Address (described below) will not be
visible.
This field should be set to Enabled only when a non Plug and Play ISA card (legacy card) that
requires non-ROM memory space is used. LAN cards that have on-board memory buffers are one
example of this; video capture cards that have video buffer memory are another.
By default, allocation of upper memory is as follows: memory from C0000-C7FFF is
automatically shadowed. (This memory range is typically reserved for video BIOS.) Memory
from C8000-DFFFFh is initially unshadowed. The BIOS scans this range for any ISA expansion
card BIOS that may be present and notes the location and size. The BIOS will then autoconfigure
the PCI and Plug and Play devices, shadowing the ROM requirements (other than video) into the
area above E0000h until that area is full. It will then assign additional PCI and Plug and Play
expansion cards to the area between C8000h and DFFFFh. If an ISA legacy card has non-ROM
memory requirements, the autoconfigure routine may write into an area that is needed by the ISA
expansion card. The ISA Shared Memory Size parameter signifies the autoconfigure routine that
this block of memory is reserved and should not be shadowed.
Shadowing is a technique that copies a block of memory from an add-in card’s ROM to the same
address in system memory. This provides faster access and achieves higher performance. By
default, all upper memory is shadowed.
3.14.10.4 ISA Shared Memory Base Address
Sets the base address for the ISA Shared Memory. The options are:
• C8000h (default)
• CC000h
• D0000h
• D4000h
• D8000h
• DC000h
This setting could affect the ISA Shared Memory Size item. The value entered in the ISA Shared
Memory Size item cannot extend to the E0000h address.
For example, if a size of 64K is selected, options D4000h, D8000h, and DC000h are not available.
If the ISA Shared Memory Size is set to Disabled, this field will not appear.