The BIOS POST memory testing is performed as follows:
The first megabyte of DRAM is tested by the BIOS before the BIOS code is shadowed (that is, copied from ROM to DRAM).
Once executing out of DRAM, the BIOS performs a simple memory test (a write/read of every location with the pattern 55aa55aa).
Note - This memory test is performed only if Quick Boot is not enabled from the Boot Settings Configuration screen. Enabling Quick Boot causes the BIOS to skip the memory test. See How to Change the POST Options for more information.
The BIOS polls the memory controllers for both correctable and non-correctable memory errors and logs those errors into the SP.
The message BMC Responding appears at the end of POST.