Hi,
I didnt even remember that the ASA5585-X supported 8.2 series software.
I am wondering if this software level only supports the amount of memory you mention. The ASA5500-X series documentation (models 5512-X to 5555-X separately mentions they run 64bit OS)
http://www.cisco.com/en/US/prod/collateral/vpndevc/ps6032/ps6094/ps6120/at_a_glance_c45-701635.pdf
We have several 5585-X SSP20 and they have the mentioned 12GB of RAM. They all run at minimum 8.4(x) software level
Hardware: ASA5585-SSP-20, 12288 MB RAM, CPU Xeon 5500 series 2133 MHz
1 CPUs, 8 cores
Naturally the jump from 8.2 would not be easy as for example the NAT configuration format changes completely.
- Jouni