CHAINTECH CT-6BJM, Руководство пользователя

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User's Manual
30
L. Shadow Memory
Software such as system BIOS, video BIOS, SCSI BIOS, etc that resides in ROM
(Read Only Memory) chips is called firmware. Shadowing of firmware occurs when
BIOS is copied to RAM address C0000h through DFFFFh. Video BIOS loads into
the C0000-C7FFF memory area when video shadowing is enabled. If an expansion
peripheral in your system contains ROM-based firmware, you need to know the
address range the ROM occupies to shadow it into the correct area of RAM.
Shadowing improves the firmware's performance because the firmware can be read
by the CPU through the 16- or 32-bit DRAM bus as opposed to the 8-bit XT bus.
However, shadowing also results in reducing the amount of high memory (640
KB to 1 MB) for loading device drivers. Shadowing is used mostly for ROM chips
on ISA cards and not for PCI cards. Shadowing and playing games at the same
time may result in system instability as some games access the RAM memory area
being shadowed.