IBM System x3850 X5 Implementation Guide

Chapter 3. IBM System x3850 X5 and x3950 X5 85
Figure 3-19 shows eight possible memory configurations for the two memory cards and 16
DIMMs connected to one processor socket. Each configuration has a relative performance
score. Note the key information from this chart:
򐂰 The best performance is achieved by populating all memory DIMMs in two memory cards
for each processor installed (configuration 1).
򐂰 Populating only one memory card per socket can result in approximately a 50%
performance degradation (compare configuration 1 with 5).
򐂰 Memory performance is better if you install DIMMs on all memory channels than if you
leave any memory channels empty (compare configuration 2 with 3).
򐂰 Two DIMMs per channel result in better performance that one DIMM per channel
(compare configuration 1 with 2, and compare configuration 5 with 6).
Figure 3-19 Relative memory performance based on DIMM placement (one processor and two memory cards shown)
Use the following general memory population rules:
򐂰 DIMMs must be installed in matching pairs.
򐂰 Each memory card requires at least two DIMMs.
򐂰 Each processor and memory card must have identical amounts of RAM.
򐂰 Install and populate two memory cards per processor or you can lose memory bandwidth.
1
Each processor:
2 memory controllers
2 DIMMs per channel
8 DIMMs per MC
Mem Ctrl 1 Mem Ctrl 2
1.0
2
Mem Ctrl 1 Mem Ctrl 2
Each processor:
2 memory controllers
1 DIMM per channel
4 DIMMs per MC
0.94
Mem Ctrl 1
Memory card
DIMMs
Channel
Memory buffer
SMI link
Memory controller
3
Mem Ctrl 1 Mem Ctrl 2
Each processor:
2 memory controllers
2 DIMMs per channel
4 DIMMs per MC
0.61
Relative
performance
4
Mem Ctrl 1 Mem Ctrl 2
Each processor:
2 memory controllers
1 DIMM per channel
2 DIMMs per MC
0.58
5
Mem Ctrl 1 Mem Ctrl 2
Each processor:
1 memory controller
2 DIMMs per channel
8 DIMMs per MC
0.51
6
Mem Ctrl 1 Mem Ctrl 2
Each processor:
1 memory controller
1 DIMM per channel
4 DIMMs per MC
0.47
7
Mem Ctrl 1 Mem Ctrl 2
Each processor:
1 memory controller
2 DIMMs per channel
4 DIMMs per MC
0.31
8
Mem Ctrl 1 Mem Ctrl 2
Each processor:
1 memory controller
1 DIMM per channel
2 DIMMs per MC
0.29
1
0.94
0.61
0.51
0.47
0.31
0.29
0.58
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
12345678
Configuration
Relative memory performance
Memory configurations

IBM System x3850 X5 Specifications

General

Processor Cores	Up to 10 cores per processor
Chipset	Intel 7500
Hard Drive Interface	SAS/SATA
Processor	Intel Xeon E7-4800 series, Intel Xeon E7-8800 series
Memory Slots	64 DIMM slots
Storage	Up to 16 x 2.5" hot-swap SAS/SATA HDDs or SSDs
RAID Support	RAID 0, 1, 5, 6, 10
Network Interface	Integrated Gigabit Ethernet
Operating System Support	Microsoft Windows Server, Red Hat Enterprise Linux, SUSE Linux Enterprise Server, VMware vSphere
Form Factor	4U Rack