I have the doubt if it's possible to bond 1 DS port with 4freq. on one MC20x20 to another DS Port with 4freq. on another MC20x20 ? The goal is to have with 2 MC20x20 LineCard 5 DS Bonding Group with 8freq. each.
From my point of view, it's not possible.
No not possible to bond across linecards.
If you want to offer 8X bonding, a typical design would be to configure each 20x20 card to have 4 service areas, with 4 "direct" DS per area. And then use your forward combiner to "span" the remaining 4 DS across all 4 service areas. This works pretty well providing both 4X and 8X bonding support.
The capacity from spanned DS are shared across the 4 service areas, catering for traffic bursts from the 8X modems. Also can be used to distribute IPTV multicast.
mbowe is right. This idea is one of the solutions from cisco to honor the circumstances that many MSO will use the potential of 8DS Channel-Bonding capable cable modems. The count of 20 DS per MC20x20 with Service-Groups with up to 8 DS will not fit perfect into the MC20x20 (2x 8DS and 1x 4DS). So the plan is to support 4 Service-Groups with each Service-Group have 4 native downstream channels and the last 4 downstream channels are shared across the 4 Service-Groups.
The problem for this solution is that the monitoring is awful. It's hard to determine from which Service-Group the traffic at the shared downstream channel is come.