Next Previous

Retired Document

Important: This document may not represent best practices for current development. Links to downloads and other resources may no longer be valid.

Expansion Features

This chapter describes the RAM expansion and the CardBus slot expansion features of the 15-inch PowerBook G4 computer.

RAM Expansion Slots

The 15-inch PowerBook G4 has two RAM expansion slots that accommodate standard SO (small outline) DIMMs using PC2-4200 DDR2 SDRAM devices. One or both slots may be occupied by factory-installed DDR2 SO-DIMMs. The slots are accessible for user installation of an additional or larger DDR2 SO-DIMM.

RAM expansion SO-DIMMs must be 200 pin, PC2-4200 DDR2 compliant.

The SO-DIMMs must use DDR2 SDRAM devices. If the user installs an SO-DIMM that uses SDR devices, the boot process will fail when the user attempts to restart the computer and the computer will not operate.

The address logic for the RAM slots supports up to 2 GB total DDR2 RAM.

Accessing the RAM Slots

The user can access the RAM expansion slots by removing the memory slot cover on the back of the computer, as shown in Figure 4-1. For complete instructions on accessing and replacing the RAM memory, refer to the 15-inch PowerBook G4 Getting Started guide that came with the computer.

**Figure 4-1** Interior view showing RAM expansion slots

Mechanical Design of DDR2 RAM SO-DIMMs

The RAM expansion modules used in the 15-inch PowerBook G4 are standard 200-pin PC2-4200 DDR2 RAM SO-DIMMs, as defined in the JEDEC specifications. The SO-DIMM runs at 333 MHz.

The mechanical characteristics of the RAM expansion DDR2 SO-DIMM are given in the JEDEC specification. To obtain a copy of the specification, see the references listed at RAM Expansion Modules.

The specification defines DDR2 SO-DIMMs with nominal heights of 1.0, 1.25, 1.5, and 2.0 inches. The 15-inch PowerBook G4 can accommodate DDR2 SO-DIMMS with heights of 1.25 inches or less.

The JEDEC specification defines the maximum depth or thickness of an SO-DIMM as 3.8 mm. Modules that exceed the specified thickness can cause reliability problems.

Electrical Design of DDR2 RAM SO-DIMMs

DDR2 SO-DIMMs for the 15-inch PowerBook G4 are required to be PC2-4200 compliant. For information, see the references at RAM Expansion Modules.

The electrical characteristics of the DDR2 RAM SO-DIMM are given in the JEDEC specification. 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.

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.

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.

DDR2 SDRAM Devices

The DDR2 SDRAM devices used in the RAM expansion modules must be self-refresh type devices for operation from a 1.8 V power supply. The speed of the SDRAM devices must be 533 MHz or higher.

The devices are programmed to operate with a CAS latency of 3 or 4. At this CAS latency the access time from the clock transition must be +/- 0.6 ns or less for data strobes and +/- 0.7 ns for data lines. The burst length must be at least 4 and the minimum clock delay for back-to-back random column access cycles must be a latency of 1 clock cycle.

When the computer is in sleep mode, the RAM modules are in self-refresh mode and the maximum power-supply current available for each RAM module is 6 mA/128 MB (see the section DDR2 RAM SO-DIMM Electrical Limits). Developers should specify SDRAM devices with low power specifications so as to stay within that limit.

Configuration of DDR2 RAM SO-DIMMs

Table 4-1 shows information about the different sizes of DDR2 SDRAM devices used in the memory modules.

**Table 4-1** Sizes of DDR2 SDRAM expansion SO-DIMMS and devices
DIMM size	Device size	Device Configuration (depth x bits x banks)	Devices per rank	Rank size	# of ranks
256 MB	256 Mbits	8 M x 8 x 4	8	256 MB	1
512 MB	256 Mbits	8 M x 8 x 4	8	256 MB	2
512 MB	512 Mbits	8 M x 16 x 4	4	512 MB	1
512 MB	512 Mbits	16 M x 8 x 4	8	512 MB	1
1 GB	512 Mbits	8 M x 16 x 4	4	512 MB	2
1 GB	512 Mbits	16 M x 8 x 4	8	512 MB	2
1 GB	1 Gbits	8 M x 16 x 8	4	1 GB	1
1 GB	1 Gbits	16 M x 8 x 8	8	1 GB	1

Address Multiplexing

Table 4-2 lists the types of devices that can be used in the 15-inch PowerBook G4.

**Table 4-2** Types of DDR2 SDRAM devices
Device size	Device configuration (depth x bits x banks)	Row address bits	Column address bits	Bank address
256 Mbits	8 M x 8 x 4	13	10	BA[0-1]
512 Mbits	8 M x 16 x 4	13	10	BA[0-1]
512 Mbits	16 M x 8x 4	14	10	BA[0-1]
1 Gbits	8 M x 16 x 8	13	10	BA[0-2]
1 Gbits	16 M x 8x 8	14	10	BA[0-2]

DDR2 RAM SO-DIMM Electrical Limits

Each DDR2 RAM SO-DIMM must not exceed the following maximum current limits on the +1.8 V supply:

Active: 1.2 A (8 devices at 150 mA each)

Sleep: 6 mA/128 MB

The Intrepid 2 memory controller does not support 4-bit-wide SDRAM devices in any RAM expansion module.

PC Card/CardBus Slot

The PC Card/CardBus slot accepts one Type I or Type II card. The slot supports both 16-bit PC Cards and 32-bit CardBus Cards. The card can be removed and replaced while the computer is operating.

Next Previous