Cisco UCS B420 M3 Installation And Service Note page 26

Memory Performance
When configuring your server, consider the following:
• DIMMs within the blade can be of different speeds, but all DIMMs will run at the speed of the DIMM with the lowest speed.
• No mixing of DIMM type (LRDIMM, RDIMM, TSV-RDIMM) is allowed.
• Your selected CPU(s) can have some affect on performance. CPUs used must be of the same type.
• Mixing DIMM ranks and densities can lower performance.
• Unevenly populating DIMMs between CPUs can lower performance.
Bandwidth and Performance
You can achieve maximum bandwidth, performance, and system memory by using the following configuration:
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