Physical server notes

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SuperMicro X11SCM: Serial ports must be enabled under "Super IO"

A brand new server with an X11SCM series board was shipped with IPMI serial-over-LAN nonfunctional. The host OS reported a single serial port on an unusual memory-mapped UART:

# dmesg
dw-apb-uart.2: ttyS0 at MMIO 0x91a1c000 (irq = 20, base_baud = 7500000) is a 16550A

# setserial -g /dev/ttyS*
/dev/ttyS0, UART: 16550A, Port: 0x0000, IRQ: 20
/dev/ttyS1, UART: unknown, Port: 0x02f8, IRQ: 3
/dev/ttyS2, UART: unknown, Port: 0x03e8, IRQ: 4
/dev/ttyS3, UART: unknown, Port: 0x02e8, IRQ: 3

but this /dev/ttyS0 did not connect to IPMI SOL, which also didn't show the BIOS console redirection output either. It turns out however that this isn't the right port (and I have no idea what it's for).

Instead, the traditional UART needs to be enabled through firmware settings under Advanced > Super IO Configuration (enabling both serial ports in that submenu), at which point ttyS0 will become the physical COM1 port, ttyS1 will become the IPMI SOL port, and the mysterious dw-apb-uart will shift to ttyS2.

# dmesg
00:02: ttyS0 at I/O 0x3f8 (irq = 4, base_baud = 115200) is a 16550A
00:03: ttyS1 at I/O 0x2f8 (irq = 3, base_baud = 115200) is a 16550A
dw-apb-uart.2: ttyS2 at MMIO 0x91a1c000 (irq = 20, base_baud = 7500000) is a 16550A

# setserial -g /dev/ttyS*
/dev/ttyS0, UART: 16550A, Port: 0x03f8, IRQ: 4
/dev/ttyS1, UART: 16550A, Port: 0x02f8, IRQ: 3
/dev/ttyS2, UART: 16550A, Port: 0x0000, IRQ: 20
/dev/ttyS3, UART: unknown, Port: 0x02e8, IRQ: 3

# systemctl edit serial-getty@ttyS1
[Service]
ExecStartPre=stty 115200
# systemctl enable serial-getty@ttyS1

SuperMicro X11SCM: Manual fan control

The "IPMI" web interface on X11SCM boards has an Optimal mode which allows fans to stay at 20% when the load is low. For a 1U server with 4 fans, that's still a bit too loud though.

The fan level can be manually controlled (as well as the automatic mode changed) using IPMI commands. They vary between models, but on this specific one, the commands are:

In the SYS-1019C-FHTN8 chassis, all four fans seemingly belong to zone 0x00.

Apr 2026