Here is the link to PD, scroll down to torrent file section and click [FREE] MAME 0.121 ROMs. Open it in a torrent client, preferably uTorrent, and d/l it. This one is completely for FREE. So you don't need to have a positive ratio to be able to d/l it.

And yes, this one includes every arcade game (6.500+, but not the CHD files). It's 16GB big, and if joining with the 120 set, it begins at 98.6%.