Chapter 7. IBM System x3690 X5 3117.4 MAX5 considerationsOn top of the half of a terabyte (TB) of memory that can be configured in the x3690 X5, anadditional half of a TB of memory can also be configured in the MAX5 memory expansion unitand attached to the server to increase overall memory access performance and capacity.MAX5 is best used with applications that can benefit from the increase in overall memorycapacity. The most significant performance gains come in applications, which require theadditional memory that MAX5 can provide. If an application does not need the extra memory,the potential for performance gains is reduced.The best way to populate memory DIMMs in the server and the MAX5 depends greatly on themanner in which the applications that are being run address memory and the total amount ofmemory that is needed by the applications. However, you also need to consider the followingrules: Always populate the DIMM sockets in the server first before installing DIMMs in the MAX5.Local memory has higher bandwidth and lower latency than MAX5 memory. MAX5memory is limited by the speed of the QuickPath Interconnect (QPI) link. If possible, install DIMMs so that Hemisphere Mode is enabled. Without HemisphereMode, performance can suffer considerably. The MAX5 can be used on an x3690 X5 that has only one processor installed. However,you get the best performance by having both processors installed and installing memory toboth the system planar and the memory mezzanine. MAX5 adds an additional path to memory through dedicated QPI ports, which results inpotentially greater memory bandwidth. There might be instances where it is better to havereserve DIMMs for use in the MAX5.7.4.1 Before you attach the MAX5Before you can attach and use the MAX5, the x3690 X5 requires that the firmware, which isshown in Table 7-2, is in place. Perform firmware updates in the order listed.Table 7-2 Minimum firmware levels to support the MAX5 memory expansionFirmware type Version Build1. IMM 1.20 YUOO75T2. UEFI 1.21 MLE120B3. FPGA 1.10 MLDU20EUSField Programmable Gate Array (FPGA) on the MAX5: The MAX5 also has FPGAfirmware that resides on it. The FPGA firmware is updated automatically when the serverto which it is attached has its FPGA firmware flashed. The default FPGA loaded onto theMAX5 from the factory is for the System x3850 X5. You are required to reflash the FPGAon your system x3690 X5 after the MAX5 is connected to it.The server might fail to complete POST because of a significant difference in FPGA codebetween the MAX5 and the server. Correct this problem by flashing the FPGA through theIMM while the server is plugged into power but not powered on.
