Check out the minimum Cisco IOS version to run on Cisco routers for using SDM:
https://www.cisco.com/c/en/us/products/collateral/routers/1800-series-integrated-services-routers-isr/prod_bulletin0900aecd806571a6.html
DRAM and file size requirements:
Cisco IOS images
https://community.cisco.com/t5/routing/about-dram-and-flash-size-requirements-for-ios-images/td-p/2394038