Recover Data from an eMMC on a Device with Bad Memory

Question

I just lost a laptop to bad RAM. I don't have anything I need to recover from it and I've already disposed of it, so for me this is just a hypothetical question.

When recovering data on a device with good RAM, you use a live Linux distribution and transfer the files to an external storage medium. On a device with bad RAM, you remove the internal storage medium and connect it to another device.

Neither of those options is available if your device uses eMMC and has bad RAM. However, it is still possible to run memtest, which does not use RAM, but still accesses it. This means, as far as I can tell, that it should be possible for a similar program to exist that can recover data from a any storage device connected to the motherboard without using RAM (if I can access the RAM, why not storage?).

So for the question: Does such a data recovery program exist, and if not, why?

Quick Edit: I just remembered badram boot parameters, so let's assume for the sake of the question that instead of the RAM being bad, its the RAM connectors on the motherboard. So RAM can't be used at all.

Quick Edit 2: I just found this question, so it seems that memtest does use RAM, so I'm not sure if there's merit in my question.

Answer 1

Memtest does use ram. badram also uses ram; it only blacklists what ram to avoid using.

There is software that can run without RAM. An example would be the very early stages of BIOS. The processor is in a Cache as RAM mode, or CRAM mode, because BIOS itself is responsible for configuring the memory parameters. There is very little cache on your processor, usually only a few MB. There is no room for any complicated software. At this point in boot, BIOS only has enough space to set up RAM, and accordingly that is the only thing it does. Once RAM is set up, then BIOS can start running larger programs to set up other parts of the system such as storage controllers and USB.

I do not know of any bootable tool that recovers data on a system with no RAM. I do not think it is possible to get the code to enable your storage controller and any other I/O device into the footprint of CRAM. Even if it was possible to compact that code down to a CRAM footprint, such a tool would also be specific to your storage controller and would only work on your specific laptop model. I do not think such a tool would ever be created.

I am not a data recovery expert, but I would suspect that the easiest way out is to remove the emmc from the system and use something else - another identical system or a diagnostic tool - to copy the data off.