Most laptops won't let you disable soldered RAM.

No, not in any straightforward way. Consumer BIOS menus almost never have an option to disable soldered memory. The system sees all RAM—soldered and socketed—as one pool, and it expects both to be present.

Even if you find a “Memory Remapping” or “Memory Configuration” setting, it’s usually for reserving space or enabling dual-channel, not for disabling individual modules. Some higher-end business or workstation laptops (like certain Lenovo ThinkPads or Dell Precision models) might have deeper BIOS options, but it’s rare and undocumented.

Worst case: you could try physically removing the socketed module to see if the system boots on soldered RAM alone. But you can’t remove soldered RAM. You’d be stuck with whatever the motherboard has.

If you’re trying to force single-channel for some reason (e.g., benchmarking or troubleshooting), you’re better off just using the socketed slot and ignoring the soldered memory—it’s still active, but the OS will use both.