[Cube] Good USB hub; RAM question

[t c k]

I found out not all unpowered USB hubs are the same.

Target has a 4x usb-ub from GE $19 that is small, has a short connecting
cable that folds into the hub and comes with a power adapter. But - in
contrast to several others I tried on my cube which do not work unpowered,
(for my flash disk for example) this hub works unpowered as well. Target to
the rescue * vbg *

RAM: my cube came with 256mb (2x128), but I also have 512mb (2x256) from my
G3 left over. The G3 RAM seems to have exactly the same mods as the
requirements for cube RAM. But it doesn't work. Cube starts up, but the
screen remains dark. What's that all about? And if it does work, can mix (2
x 256, 1 x 128)?

TIA,
-tobias.