
Intel
82845MP/82845MZ Chipset-Mobile (MCH-M)
250687-002
Datasheet
61
R
3.7.18.
DRC – DRAM Controller Mode Register – Device #0
Offset:
7C-7Fh
Default:
00000000h
Access:
Read/Write
Size:
32 bits
Bit
Description
31:30
Revision Number (REV): Reflects the revision number of the format used for DDR register
definition. Currently, this field must be “00”, since this (rev “00”) is the only existing version of the
specification.
29
Initialization Complete (IC): This bit is used for communication of software state between the
memory controller and the BIOS. BIOS sets this bit to 1 after initialization of the DRAM memory
array is complete.
28
Dynamic Power-down mode Enable: When set, the DRAM controller will put pair of rows into
power down mode when all banks are pre-charged (closed). Once a bank is accessed, the relevant
pair of rows is taken out of Power Down mode.
The entry into power down mode is performed by de-activation of CKE. The exit is performed by
activation of CKE.
0:
DRAM Power-down disabled
1:
DRAM Power-down enabled
27:24
Active DDR Rows: Implementations may use this field to limit the maximum number of DDR rows
that may be active at once.
0000
All rows allowed to be in the active state
Others:
Reserved.
23:22
Reserved
21:20
DRAM Data Integrity Mode (DDIM): These bits select one of 4 DRAM data integrity modes.
DDIM Operation
00
Non-ECC mode
10
Error checking with correction.
Other
Reserved
19:11
Reserved
10:8
Refresh Mode Select (RMS): This field determines whether refresh is enabled and, if so, at what
rate refreshes will be executed.
000:
Refresh disabled
001:
Refresh enabled. Refresh interval 15.6 Sec
010:
Refresh enabled. Refresh interval 7.8 sec
011:
Refresh enabled. Refresh interval 64 sec
111:
Refresh enabled. Refresh interval 64 clocks (fast refresh mode)
Other:
Reserved
7
Reserved