In order to find out whether the PA-500 has 1GB RAM or 2GB RAM, run the command "show system resources"
admin@PA-500> show system resources
top - 05:23:04 up 17 days, 6:21, 0 users, load average: 0.00, 0.03, 0.00
Tasks: 89 total, 1 running, 88 sleeping, 0 stopped, 0 zombie
Cpu(s): 2.0%us, 3.6%sy, 6.5%ni, 87.8%id, 0.0%wa, 0.0%hi, 0.1%si, 0.0%st
Mem: 2028576k total, 1972820k used, 55756k free, 154316k buffers
Swap: 2212876k total, 3320k used, 2209556k free, 769132k cached
The above output shows that the device has 2GB RAM.
If the firewall had 1GB ram this field would show Mem: 938136k.