Hi Rod,
You can find most of this information in the
BlackDiamond 8800 datasheet, in
Figure 2: Connectivity Options by I/O Module and
Figure 4: MSM Module Options.
Essentially, with two 8900-MSM128's, you can get up to 128 Gbps throughput on an 8810 chassis, and up to 80 Gbps on an 8806 chassis for both of these cards (8900-10G24X-c and 8900-10G8X-xl). The primary difference is that the XL module has larger table sizes, and will not be oversubscribed. The 8900-10G24X-c will be oversubscribed by a factor of 1.875 with two 8900-MSM128's in an 8806 chassis, and oversubscribed by a factor of 3 in an 8810 chassis.
-Brandon