After further research, I found that a 2911 would only have 1 DIMM slot for expanded memory.
I am still looking for a command that might display the information. Perhaps it did not show up because I have not yet tried it on a 2x DIMM device?
Answer found here:http://www.cisco.com/en/US/prod/collate ... _Item.html
Q. Are there any restrictions with the memory modules for the new platforms?
A. The Cisco 1900, 2900, and 3900 Series Integrated Services Routers ship with higher default memory (both DRAM and Compact Flash) than today's integrated services routers. The Cisco 2951, 3925, 3925E, 3945, and 3945E routers have two modular dual-inline-memory-module (DIMM) slots for error-correcting code (ECC) double-data-rate 2 (DDR2) synchronous dynamic random access memory (SDRAM)-each slot capable of integrating 512 MB to 2 GB DIMM.
The Cisco 3900 Series uses symmetrical DIMM modules for increased performance, meaning that two identical DIMM modules must be installed into both DIMM slots at all times. By default, the Cisco 3925, 3925E, 3945, and 3945E ship with 1 GB of system DRAM consisting of two 512-MB DIMM modules. For the Cisco 2951, the default DRAM is 512 MB installed in a single DIMM slot. Any additional memory upgrades on the Cisco 2951 can be inserted into the second DIMM slot that is open and available.
In contrast, the Cisco 1941, 1941W, 2901, 2911, and 2921 routers ship with default DRAM soldered on the main system board and one modular DIMM slot for memory upgrades; therefore, no DIMM module will be installed in these systems when ordered with default DRAM. The default DRAM is 256 MB for the Cisco 1941 and 512 MB for the Cisco 2901, 2911, 2921, and the memory upgrade for the second DIMM can range from 512 MB to 2 GB.