Electrical Design of RAM SO-DIMMs

SO-DIMMs for PowerBook G4 computer are required to be PC133 compliant. For information about the PC133 specifications, see the references at "RAM Expansion Modules".

The electrical characteristics of the RAM SO-DIMM are given in section 4.5.6 of the JEDEC Standard 21-C, release 7. To obtain a copy of the specification, see the references listed at "RAM Expansion Modules".

The JEDEC and Intel specifications define several attributes of the DIMM, including storage capacity and configuration, connector pin assignments, and electrical loading. The specifications support SO-DIMMs with either one or two banks of memory.

Important

The memory controller on the PowerBook G4 computer uses a separate CKE signals for each bank, as called out in the JEDEC specification. SO-DIMMs that have all the CKE pins connected together will not operate properly.

The JEDEC specification for the SO-DIMM defines a Serial Presence Detect (SPD) feature that contains the attributes of the module. SO-DIMMs for use in PowerBook computers are required to have the SPD feature. Information about the required values to be stored in the presence detect EEPROM is in section 4.1.2.5 and Figure 4.5.6–C (144 Pin SDRAM SO–DIMM, PD INFORMATION) of the JEDEC standard 21-C specification, release 7.

Important

For a DIMM to be recognized by the startup software, the Serial Presence Detect (SPD) feature must be programmed properly to indicate the timing modes supported by the DIMM.

Capacitance of the data lines must be kept to a minimum. Individual DRAM devices should have a pin capacitance of not more than 5 pF on each data pin.

"SDRAM Devices"

"Configuration of RAM SO-DIMMs"

"Address Multiplexing"