IBM Type 7977 manual Minimum configuration one pair of DIMMs

Minimum configuration: one pair of DIMMs

(Branch 0 works independently of Branch 1)
BR1	BR0

CH3	CH2		CH1	CH0
				Rank 0
DIMM 10	DIMM	7	DIMM 4	DIMM 1

Rank 1

Rank 1 is sparing to Rank 0

A pair of two identical double rank modules: same size, speed, and organization

DIMM 11

DIMM 12

DIMM 8

DIMM 9

DIMM 5

DIMM 6

DIMM 2

DIMM 3

Other Configuration: Multiple Pairs of DIMMs

(Branch 0 works independently of Branch 1)
BR1	BR0

CH3	CH2		CH1	CH0
			Rank 0 512 MB
DIMM 10	DIMM	7	DIMM 4	DIMM 1
			Rank 1 Empty

				Rank 2 512 MB
DIMM 11		DIMM 8	DIMM 5		DIMM 2
				Rank 3 512 MB
				Rank 4 1 GB
DIMM	12	DIMM 9	DIMM 6		DIMM 3
				Rank 5 Empty

Rank 4 is used to spare any defective rank of rank 0, 2, and 3

A pair of two identical single rank modules (512MB)

A pair of two identical double rank modules (1GB)

A pair of two identical single rank modules (1GB)

-A rank is defined as an area or block of 64 bits that is created by using some or all of the chips on a DIMM. For an ECC DIMM, a memory rank is a block of 72 data bits (64 bits plus 8 ECC bits).

-The minimum memory configuration is two single-rank DIMMs that are installed in branch 0, DIMM connector 1 (in channel 0) and connector 4 (in channel 1); however, online-sparing is not supported with this configuration.

-To support online-sparing in branch 0, you must add a second pair of DIMMs. The spare pair of DIMMs can be single-rank or double-rank and must be the same speed, type, size (or larger), and technology as the failed pair of DIMMs. The spare pair must be installed in branch 0, DIMM connector 2 (in channel 0) and connector 5 (in channel 1). Branch 0 and branch 1 operate independently.

v The following notes apply when the server operates in non-mirroring mode (normal mode):

–DIMMs must be installed in matched pairs. If you install a second pair of DIMMs in DIMM connector 7 and DIMM connector 10, they do not have to be the same size, speed, type, and technology as the DIMMs in DIMM connector

14IBM System x3500 Type 7977: Installation Guide