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Bitfields for Intel 82437,82439HX/TX,82443BX/EX/LX SMRAM control register

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Bit Description

7

 reserved

6

 SMM Space Open
1 = make SMM DRAM visible even when not in SMM if bit 4 =0

5

 SMM Space Closed
1 = no data references permitted to SMM DRAM even in SMM

4

 SMM Space Locked
1 = force bits 4 and 6 to become read-only; and clear bit 6

3

 SMRAM Enable
1 = 128K DRAM are accessible for use at A000 while in SMM

2 - 0

 SMM Space Base Segment
000 = reserved
001 = reserved
010 = segment A000-BFFF
011 = reserved
100 = segment C000-CFFF (82437MX,82443EX only)
101 = reserved
110 = reserved
111 = reserved

Note:

Bits 5 and 6 must never both be set at the same time.

See Also:

#01099,#01108,#01098,#01124,#01106,#01107,#01142,#01129