301467-005 Datasheet, PDF (102/426 Pages) Intel Corporation – Express Chipset

MCHBAR Registers
R
5.1.9
C0DRT1—Channel A DRAM Timing Register
MMIO Range:
Address Offset:
Default Value:
Access:
Size:
MCHBAR
114h
900122hh
R/W, RO
32 bits
Bit
31:24
23:20
19
18:10
9:8
7
Access &
Default
R/W
9h
RO
0b
R/W
01b
Description
Reserved
Activate to Precharge delay (t_RAS). This bit controls the number of DRAM clocks
for t_RAS. Minimum recommendations are beside their corresponding encodings.
0h – 3h = Reserved
4h – Fh = Four to Fifteen Clocks respectively.
Reserved for Activate to Precharge Delay (t_RAS) MAX: It is required that the
Panic Refresh timer be set to a value less than the t_RAS maximum. Based on this
setting, a Panic Refresh occurs before T_RAS maximum expiration and closes all
the banks.
This bit controls the maximum number of clocks that a DRAM bank can remain
open. After this time period, the DRAM controller will guarantee to pre-charge the
bank. This time period may or may not be set to overlap with time period that
requires a refresh to happen.
The DRAM controller includes a separate t_RAS-MAX counter for every supported
bank. With a maximum of four ranks, and four banks per rank, there are 16
counters per channel.
0 = 120 microseconds
1 = Reserved
Note: This register will become Read Only with a value of 0 if the design does
not implement these counters.
t_RAS-MAX is not required because a panic refresh will close all banks in a rank
before t_RAS-MAX expires.
Reserved
CASB Latency (tCL). This value is programmable on DDR2 DIMMs. The value
programmed here must match the CAS Latency of every DDR2 DIMM in the
system.
Encoding DDR CL
DDR2 CL
00
3
5
01
2.5
4
10
2
3
11
Reserved
Reserved
Reserved
102
Datasheet