You probably can't disable soldered RAM in BIOS.

No, not really.

Most laptop BIOS/UEFI firmware doesn’t give you the option to disable soldered RAM. The system detects all installed memory—soldered and socketed—and tries to use it together. If the soldered module fails, the machine typically won’t boot at all, or it will throw errors and refuse to POST.

A few business-class laptops (like older ThinkPads or Latitudes) have a “Memory Test” or “Memory Disable” option in BIOS, but those are rare and usually reserved for service diagnostics, not permanent disabling. Even if you could disable it, a failed soldered module might still cause the motherboard to fail to initialize memory channels properly.

Bottom line: if your soldered RAM dies, you’re often looking at a motherboard replacement, not a simple BIOS tweak. This is exactly why “soldered RAM is a terrible idea” applies to anything you expect to keep running for years.