w83c554f Winbond Electronics Corp America, w83c554f Datasheet - Page 64

• Manufacturer Part Number: w83c554f
• Description: System I/o Controller With Pci Arbiter & Ultradma/33 Ide Controller
• Manufacturer: Winbond Electronics Corp America

W83C554F
ISA-to-PCI Address Decoder Control Register (default = 01h)
Type:
Bit Description:
WINBOND ELECTRONICS CORP. AMERICA
Bits [7:4]:
Bit 3:
Bit 2:
Bit 1:
Bit 0:
Read/Write
IPATOM [3:0]. Top of Main Memory. Defines the top of memory for ISA memory space. ISA
memory accesses from 1 MByte to top of memory (except "hole") and above 16 MByte are
forwarded to the PCI bus.
MBELBIOS. Low BIOS Memory Block Enable; 896-960 KByte (E0000-EFFFFh). When set to
"1", ISA memory accesses in this range are forwarded to the PCI bus. The LBIOSCSE bit
(UBCSA, configuration register 4Dh bit 6) overrides this bit.
MBEVGA. VGA Memory Block Enable; 640-768 KByte (A0000-BFFFF). When set to "1", ISA
memory accesses in this range are forwarded to the PCI bus.
MBE640. Memory Block Enable; 512-640 KByte (80000-9FFFFh). When set to "1", ISA
memory accesses in this range are forwarded to the PCI bus.
MBE512. Memory Block Enable; 0-512 KByte (0-7FFFFh). When set to "1", ISA memory
accesses in this range are forwarded to the PCI bus. This bit is set to "1" after reset.
Bit 7
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
Bit 6
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
Bit 5
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
Bit 4
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
Top of Memory
1 MByte
2 MByte
3 MByte
4 MByte
5 MByte
6 MByte
7 MByte
8 MByte
9 MByte
10 MByte
11 MByte
12 MByte
13 MByte
14 MByte
15 MByte
16 MByte
Register Information
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