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AMD-761™ System Controller Programmer’s Interface
Chapter 2
AMD-761™ System Controller Software/BIOS Design Guide
24081D—February 2002
Preliminary Information
Programming Notes
Note that these registers are not initialized at reset time, but must be initialized by BIOS for proper operation. This action
should be done prior to attempting DRAM access. Table 11 shows DRAM addressing modes.
Bit Definitions
Memory Base Address Registers 0–7 (Dev0:F0:0xC0–0xDF)
Bit
Name
Function
31–23
CS_Base
Chip-Select Base
This bit field defines which 8-Mbyte boundary the given bank services. Incoming
addresses are compared against field, subject to the mask field in bits [15:7].
22–16
Reserved
Reserved
15–7
CS_Mask
Chip-Select Mask
This bit field defines what bits in the address are ignored when incoming addresses are
compared to the CSBase in bits[31:23] above. If a given bit is set, the corresponding bit in
the compare is ignored.
6–3
Reserved
Reserved
2–1
Addr_Mode
Addressing Mode
This bit field determines the addressing mode for this CS, based on the type of DIMM
installed, according to Table 11. This addressing applies to the physical addressing on the
MAA and MAB address buses.
Note that modes 00 and 11 are reserved
.
0
CS_En
Chip-Select Enable
When set, this bank is eligible for selection by incoming addresses. When clear, this bank’s
chip select is not asserted and the values in [31:23] and [15:7] are ignored.
Table 11.
AMD-761™ DRAM Addressing Modes
Mode
Pins
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Mode 1
Addr_Mode = 01
64 Mbyte x4/8/16
128 Mbyte x4/8/16
Row
12
11
24
23
22
21
20
19
18
17
16
15
14
13
Col
12
11
27
PC
26
25
10
9
8
7
6
5
4
3
BK
BK
Mode 2
Addr_Mode = 10
256 Mbyte x4/8/16
512 Mbyte x4/8/16
Row
12
11
25
24
23
22
21
20
19
18
17
16
15
14
13
Col
12
11
29
28
PC
27
26
10
9
8
7
6
5
4
3
BK
BK