TRMから引用。まぁ必要なこともある、って感じだけど、メモリなんてグラボに比べたら安いので8G積んでて損はない。
グラボが多い時の多いってのがどれぐらいをTRMの人たちが想定しているのか知らんw

Host ram requirements is minimum 4GB, but we have heard about some systems
needing an upgrade to 8GB when using B/C-modes across many gpus. At the time of
writing, we don't know exactly why and when this is needed, but if you
experience instant hard crashes when allocating large amounts of vram on all
gpus and have an extra ram stick lying around, try increasing host ram on the
rig in question.