From:    Arnt Karlsen <arnt@???>

Date:    Mon, 30 Jun 2025 07:17:11 +0200

> Chances are you have such cable tools ...

All I have is one or two null modem cables with DE-9 subminiature
connectors. Should suffice to connect an old machine with a DE-9
serial port and terminal emulator. I expect no difficulty with the
connection and the terminal emulator.

> if you've ever messed around flashing new firmware onto things
> like cameras, rc radios, autopilots or laptop bios chips, etc.

Zero! =8~/ I expect that tracing should begin with GRUB.
https://www.gnu.org/software/grub/manual/grub/html_node/Serial-terminal.html

As mentioned previously, the machine has no built-in serial port or
headers.

If a PCIe serial adapter is added, the serial port is configured as
described here.
https://www.gnu.org/software/grub/manual/grub/html_node/serial.html#serial

Alternatively a USB adapter can be added with configuration as here.
https://unix.stackexchange.com/questions/79838/grub-and-usb-serial-support
More modules to load and more complex than for the PCIe adapter.

With no intended offense to your preference for USB, isn't the PCIe
adapter the simpler option?

Thanks,                          ... P.

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