Cisco ASA 5520 Memory Upgrade

For anyone using a Cisco ASA 5505, 5510, 5520 or 5540 in their home, lab or non-production environments and wants to be able to run ASA OS versions 8.3 and later you’re probably going to be on the market for a memory upgrade. Cisco ASA memory upgrades are bonkers expensive and while for a production environment you’d want to pay this to get the Cisco TAC support, chances are you aren’t going to want to stump up this kind of money for other purposes.

There is an exception to this rule is if you happen to have an ASA whereby it was either built after February 2010 or the previous owner upgraded it but that’s neither here nor there.

The specifications from Cisco on the memory requirements for each model to run ASA OS 8.3 or later and the comparative shipping memory values can be found at

In my case, the ASA 5520 shipped originally with 512MB of RAM but for ASA OS 8.3 or later you need to have 2GB. The ASA 5520 varies in it’s hardware configuration according to age with some models having four DIMM slots and others only having two. If you’ve got an ASA 5520 or 5540 with only one DIMM slot then sorry, you’ve got an ASA 5510 which has been faked into a 5520 which was a big problem at the time (

As I didn’t want to spend £300 on the memory upgrade for mine, I went on a search of the internet as you’d expect of me. It transpires that Cisco used memory from Smart Modular in the ASA appliances. 184-pin PC2700 DDR-333 ECC Unbuffered memory to be exact. According to some clever people on the internet, not many memory modules aside from these from Smart will work in the ASA as the Linux kernel on it is only coded to recognise a select few memory setups however luckily, it appears that Infineon are one of the good guys.

Due to the way that memory under-rates itself when required, you don’t have to stick to PC2700 DDR-333 and nor does it seem that you need ECC memory either. From advice online I’ve found that the following module models from Infineon work great in the ASA 5520. I’ve had none of the commonly reported issues with third-party memory of the appliance only successfully booting one in two or three reload cycles. My ASA has booted first time, every time and I’ve been cycling it about once and hour today to test it.

If you’ve got the luxury of four DIMM slots, go with the Infineon HYS64D64320HU-5-C. It’s a 512MB PC3200 DDR-400 DIMM which you can install four of to make the 2GB requirement. If you’ve only got the two DIMM slots to play with, go with the Infineon HYS64D128320HU-5-B which is a 1GB PC3200 DDR-400 DIMM.

eBay is the place to buy in case there was any doubt over that point and no matter which one of the above options you go with, by using these Infineon DIMM modules, you’ll get a reliable ASA platform and it allows you to hit your memory maximums for ASA OS 8.3 and onwards for about £20 at the time of writing. Just a touch better than the £300 for the official memory right?


Richard works as a Cloud Consultant for Fordway Solution where his primary focus is to help customers understand, adopt and develop with Microsoft Azure, Office 365 and System Center. Richard Green is an IT Pro with over 15 years' of experience in all things Microsoft including System Center and Office 365. He has previously worked as a System Center consultant and as an internal solutions architect across many verticals. Outside of work, he loves motorbikes and is part of the orange army, marshaling for NGRRC, British Superbikes and MotoGP. He is also an Assistant Cub Scout Leader.