Datasheet

Functional Description
108 Intel
®
82845G/82845GL/82845GV GMCH Datasheet
4.2.3 Memory Organization and Configuration
In the following discussion the term “row” refers to a set of memory devices that are
simultaneously selected by a chip select signal. The GMCH supports a maximum of 4 rows of
memory. For the purposes of this discussion, a “side” of a DIMM is equivalent to a “row” of
SDRAM devices.
The memory bank address lines and the address lines allow the GMCH to support 64-bit wide x8
and x16 DIMMs using 64-Mb, 128-Mb, 256-Mb, and 512-Mb SDRAM technology.
For the DDR SDRAM interface, Table 4-2 lists the supported DDR DIMM configurations. Note
that the GMCH supports configurations defined in the JEDEC DDR DIMM specification only
(A,B,C). Non-JEDEC standard DIMMs (e.g., double-sided x16 DDR SDRAM DIMMs) are not
supported. For more information on DIMM configurations, refer to the JEDEC DDR DIMM
specification.
For the SDR SDRAM interface, Table 4-3 lists the supported SDR DIMM configurations.
Note: Mixed mode or uneven, double-sided SDR SDRAM DIMMs are not supported.
4.2.3.1 Configuration Mechanism for DIMMs
Detection of the type of SDRAM installed on the DIMM is supported via Serial Presence Detect
(SPD) mechanism as defined in the JEDEC DIMM specification. This uses the SCL, SDA, and
SA[2:0] pins on the DIMMs to detect the type and size of the installed DIMMs. No special
programmable modes are provided on the GMCH for detecting the size and type of memory
installed. Type and size detection must be done via the serial presence detection pins and is
required to configure the GMCH.
Table 4-2. Supported DDR DIMM Configurations
Density 64 Mbit 128 Mbit 256 Mbit 512 Mbit
Device
Width
X8 X16 X8 X16 X8 X16 X8 X16
Single /
Double
SS/DS SS/DS SS/DS SS/DS SS/DS SS/DS SS/DS SS/DS
184 pin
DDR
DIMMs
64 MB /
128 MB
32 MB /
NA
128 MB /
256 MB
64 MB /
NA
256 MB /
512 MB
128 MB /
NA
512 MB /
1024 MB
256 MB/
NA
Table 4-3. Supported SDR DIMM Configurations
Density 64 Mbit 128 Mbit 256 Mbit 512 Mbit
Device
Width
X8 X16 X8 X16 X8 X16 X8 X16
Single /
Double
SS/DS SS/DS SS/DS SS/DS SS/DS SS/DS SS/DS SS/DS
168 pin
SDR
DIMMs
64 MB /
128 MB
32 MB /
64 MB
128 MB /
256 MB
64 MB /
128 MB
256 MB /
512 MB
128 MB /
256 MB
512 MB /
1024 MB
256 MB /
512 MB