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RAM Expansion

This chapter describes the RAM expansion modules supported by Mac mini.

RAM Expansion

The Mac mini has one RAM expansion slot that accepts standard DDR333 PC2700, 184-pin DIMMs (dual inline memory modules) for use with SDRAM devices. The Mac mini supports DIMM sizes 256 MB, 512 MB, or 1 GB of memory for a total system maximum of up to 1 GB.

RAM Expansion Modules

The RAM expansion modules for the Mac mini are 184-pin SDRAM DIMMs that are 2.5 volt, unbuffered, 8-byte, non-parity, and PC2700 compliant. The speed of the SDRAM devices must be rated at 167 MHz or faster.

Mechanical Design of RAM DIMMs

The mechanical characteristics of the RAM expansion DIMM are given in the JEDEC specification for the 184-pin 8-byte DRAM DIMM. The specification number is JEDEC MO-161-D. To obtain a copy, see the reference information at RAM Expansion Modules.

The maximum height of DIMMs for use in the Mac mini is 1.50 inches.

Electrical Design of RAM DIMMs

The electrical characteristics of the RAM DIMM are given in section 4.5.6 of the JEDEC Standard 21-C. The specification is available from the Electronics Industry Association’s website. The specification defines several attributes of the DIMM, including storage capacity and configuration, connector pin assignments, and electrical loading. To obtain a copy, see the reference information at RAM Expansion Modules.

The presence detect serial EEPROM specified in the JEDEC standard is required and must be set to properly define the DIMM configuration. Details about the required values to be stored in the presence detect EEPROM can be found in sections 4.5.4 and 4.1.2.5 of the JEDEC standard 21-C specification.

The RAM DIMMs are required to be PC2700 compliant. To obtain information about the PC2700 specification, see the reference information at RAM Expansion Modules.

The SDRAM devices used in the RAM expansion modules must be self-refresh type devices for operation from a 2.5 V power supply.

DIMM Configurations

The largest DIMM supported is a two-bank DIMM of 1 GB using 512 Mbit using SDRAM devices. The largest bank size supported by the memory controller is 512 MB. The maximum number of devices per DIMM is 16. CAS latency is 2.5.

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

**Table 4-1** Sizes of DDR SDRAM expansion DIMMS and devices
Size of DIMM	SDRAM device size	Device configuration	Devices per bank	number of banks
256 MB	256 Mbits	8 M x 8 x 4	8	1
512 MB	256 Mbits	8 M x 8 x 4	8	2
512 MB	512 Mbits	16 M x 8 x 4	8	1
1 GB	512 Mbits	16 M x 8 x 4	8	2

The Mac mini accepts only one DIMM. Any of the supported DIMM sizes can be installed in the slot.

RAM Addressing

Signals A[0] – A[12] and BA[0] – BA[1] on each RAM DIMM make up a 15-bit multiplexed address bus that can support several different types of SDRAM devices.

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