[micrex22]

http://aix.software.ibm.com/aix/efixes/s...visory.asc

As mentioned in IBM's advisory, there were multiple releases for AIX to fix spectre/meltdown vulnerabilities. Here are the direct links from the advisory:

The AIX/VIOS fixes can be downloaded via ftp or http from:

• ftp://aix.software.ibm.com/aix/efixes/se...wn_fix.tar
  
• http://aix.software.ibm.com/aix/efixes/s...wn_fix.tar
  
• https://aix.software.ibm.com/aix/efixes/...wn_fix.tar
  

It's worth noting AIX is most likely not going to really be affected by meltdown since branch predictor cache can't directly access kernel data structures (like it would in Linux or Windows or whatever). But security is always important.

IBM is of course still supporting 5.3 (which is great), but I believe you need the latest patches to bring it up to 5.3.12.9 before the spectre/meltdown patch can be applied. Supposedly these patches are generally added into virtual machines running 5.3 (rather than on baremetal), but I do intend to test them out on the 185 when I have the chance of getting it set up.