I bought a pair of 512MB memory to upgrade my ASA5505 security plus pair. There are many posts online which people had successfully upgraded their ASA5505 to 1GB. For ASA OS 8.4 to work on ASA5505 a minimum requirement of 512MB is required.
My old ASA5505 pair is usign 256MB and running on ASA OS 8.2 and ASDM 6.21. With ASA OS 8.4 ASA5505 will have to use ASDM 6.43.
License features difference
ASA 8.2
Maximum Physical Interfaces : 8 VLANs : 20, DMZ Unrestricted Inside Hosts : 10 Failover : Active/Standby VPN-DES : Enabled VPN-3DES-AES : Enabled SSL VPN Peers : 2 Total VPN Peers : 25 Dual ISPs : Enabled VLAN Trunk Ports : 8 Shared License : Disabled AnyConnect for Mobile : Disabled AnyConnect for Linksys phone : Disabled AnyConnect Essentials : Disabled Advanced Endpoint Assessment : Disabled UC Phone Proxy Sessions : 2 Total UC Proxy Sessions : 2 Botnet Traffic Filter : Disabled
ASA 8.4
Licensed features for this platform: Maximum Physical Interfaces : 8 perpetual VLANs : 20 DMZ Unrestricted Dual ISPs : Enabled perpetual VLAN Trunk Ports : 8 perpetual Inside Hosts : 10 perpetual Failover : Active/Standby perpetual VPN-DES : Enabled perpetual VPN-3DES-AES : Enabled perpetual AnyConnect Premium Peers : 2 perpetual AnyConnect Essentials : Disabled perpetual Other VPN Peers : 25 perpetual Total VPN Peers : 25 perpetual Shared License : Disabled perpetual AnyConnect for Mobile : Disabled perpetual AnyConnect for Cisco VPN Phone : Disabled perpetual Advanced Endpoint Assessment : Disabled perpetual UC Phone Proxy Sessions : 2 perpetual Total UC Proxy Sessions : 2 perpetual Botnet Traffic Filter : Disabled perpetual Intercompany Media Engine : Disabled perpetual
show version
ciscoasa# sh version Cisco Adaptive Security Appliance Software Version 8.4(1) Device Manager Version 6.4(3) Compiled on Mon 31-Jan-11 02:11 by builders System image file is "disk0:/asa841-k8.bin" Config file at boot was "startup-config" ciscoasa up 34 secs Hardware: ASA5505, 512 MB RAM, CPU Geode 500 MHz Internal ATA Compact Flash, 128MB BIOS Flash M50FW016 @ 0xfff00000, 2048KB
cyruslab 
Great..!!!!!!!!
Thanks bro 😀
FYI everyone, Kingston/Crucial/Etc RAM is not a sure bet as they often change silicon manufacturers. I picked up a 1G Kingston DIMM that has Elpida chips and it doesn’t work. Likewise with Micron chips (Crucial). The ASA BIOS recognized the Micron chips but the tailored Linux kernel Cisco uses for the ASA5505 8.4(3) image only has Infineon/Qimonda identifiers coded and rejects anything else. An Infineon HYS64D128320HU-5-B ($20) DIMM will definitely work. That’s something like $200 cheaper than the Cisco part.
Thanks for sharing this valuable information 🙂
Bought 4 1 GB PC3200 DDR400 mem sticks from a Goodwill Computer store in Houston. One of the four actually worked in my ASA5505 running ASA 9.1 and ASDM 7.1. I see all 1024MB in its wonderful glory.
My 5505 v09 uses a Micron Technology MT8VDDT6464AY-40BF4 512MB SIMM without any issues.