Select the AIX 6.1 version; if the exact Technology Level (TL) you need isn't listed, download the closest base media and update it later via Fix Central. IBM Fix Central : Used for downloading updates, Technology Levels (TLs), and Service Packs (SPs)
Websites like archive.org , legacy UNIX forums, or FTP mirrors may host AIX 6.1 images. Always verify checksums (MD5/SHA) against known IBM values. Unofficial ISOs can contain modified binaries, rootkits, or corrupted filesystems.
To download or update media, you must use official IBM portals, as IBM Support does not provide these images directly through standard support cases. Official Download Portals