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 |
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.
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 |
|
