Many To Many Plugin Template Help
So, if I understand you correctly, you're trying to use the Model IDs channel as a middle man? If so, I think you would just need two steps:

To get all SSDs from a Memory Entry

{% set modelIDs = craft.entries.section('MODEL ID SECTION HANDLE').relatedTo(entry).ids() %}
{% set ssds     = craft.entries.section('SSDS SECTION HANDLE').relatedTo(modelIDs).all() %}


To get all Memory from an SSD Entry

{% set modelIDs = craft.entries.section('MODEL ID SECTION HANDLE').relatedTo(entry).ids() %}
{% set memory   = craft.entries.section('MEMORY SECTION HANDLE').relatedTo(modelIDs).all() %}