The Double Data Rate 2 (DDR2) memory interface supports
up to 8GB of memory and can operate as either a single-channel
or dual-channel interface. Each of the channels (A and
B) terminates in two dual in-line memory module (DIMM)
sockets. The System BIOS automatically detects memory
type, size and speed.
The SHB uses industry standard 72-bit wide ECC gold
finger memory modules in four 240-pin sockets. The DIMMs
must be PC2-3200 compliant and have the following features:
- 240-pin with gold-plated contacts
- ECC (72-bit) DDR2 memory
- Dual rank or single rank DIMMs
- Registered configuration
The following DIMM sizes are supported:
| DIMM Size |
DIMM Type |
ECC |
| 256 MB |
Registered |
32M x 72 |
| 512 MB |
Registered |
64M x 72 |
| 1 GB |
Registered |
128M x 72 |
| 2 GB |
Registered |
256M x 72 |
NOTE: With the bracket
end of the board to the right, the DIMM sockets are
numbered 1B, 1A, 2B and 2A, from top to bottom. All
memory modules must have gold contacts.
Populating identical DIMMs in pairs (one each in the
A and B channels) results in dual- channel operation.
In dual-channel mode, the DIMM pair operates in lockstep,
theoretically doubling the memory bandwidth.
When a single DIMM is used, it should be installed
in DIMM socket 1B. With this configuration, the interface
operates as a single-channel interface with a theoretical
memory bandwidth of 3.2GB/s.
Installing two DIMMs which are identical in type, size
and rank in DIMM sockets 1B and 1A results in dual-channel
operation, which doubles the theoretical memory interface
bandwidth to 6.4GB/s. Installing additional DIMMs in
sockets 2B and 2A also results in the higher bandwidth.
In this case, the DIMMs installed in sockets 2B and
2A must be identical in type, size and rank to each
other, but may be different in size from the pair installed
in sockets 1B and 1A. If the modules in channel B and
channel A (e.g., 1B and 1A) differ in size, the BIOS
will use the size of the smallest DIMM.
Installing DIMMs only in sockets 1B and 2B results
in single-channel mode, since both DIMMs are in the
B channel. If the DIMMs are identical in type and size,
they should be populated in sockets 1B and 1A to operate
in dual-channel mode.
NOTE: The SLT supports
a DDR2-400 memory interface speed. If modules of higher
speeds are used, they will clock down to a DDR2-400
memory interface speed.
DDR2 memory modules are available as either single
rank or dual rank DIMMs. A rank refers to the 72-bit
unit of devices or DRAM chips that make up the PC2-3200
ECC registered 240-pin DDR2 DIMM. Single or dual rank
memory modules must be placed in the SHB's DIMM sockets
using prescribed population rules to ensure proper memory
interface operation and performance.
The following table explains the DDR2 DIMM population
rules:
|
DIMM Socket |
|
1B
(top-most DIMM) |
1A |
2B |
2A |
| 1 Single Rank |
Single Rank |
Empty |
Empty |
Empty |
| 1 Dual Rank |
Dual Rank |
Empty |
Empty |
Empty |
| 2 Single Rank |
Single Rank |
Single Rank |
Empty |
Empty |
| 1 Dual Rank, 1 Single Rank |
Dual Rank |
Single Rank |
Empty |
Empty |
| 2 Dual Rank |
Dual Rank |
Dual Rank |
Empty |
Empty |
| 3 Single Rank |
Single Rank |
Single Rank |
Single Rank |
Empty |
| 1 Dual Rank, 2 Single Rank |
Dual Rank |
Single Rank |
Single Rank |
Empty |
| 4 Single Rank |
Single Rank |
Single Rank |
Single Rank |
Single Rank |
|
