So, you’ve got Civil 3D 2011 and a screaming 64-bit system. How much RAM can you throw at that thing? Well, it depends on a couple things, first of all, what operating system are you running? If you’re running a 32-bit OS, then 4 gigs is your limit. There are numerous posts and discussions on the subject, just do a Google search and you’ll see.

Now, if you have a 64-bit operating system, that’s a completely different story. As I was doing a bit of research for this, I learned quite a few new things. The reason a 32-bit operating system is limited to 4 gigs of ram, is due to it’s architecture. A 32-bit system can only process 2^32 bytes of information, hence the 4-gig limit. Now, a 64-bit system can process 2^64 bytes of information. How much is that, well it’s 16 to 18 Exabytes (depending on your definition of an Exabyte). Great, but what is an Exabyte? Well, one Exabyte is a thousand petabytes, one million terabytes, or one billion gigabytes. Can you imagine having a computer with 16,000,000,000 gigabytes of RAM? We as humans really can’t comprehend large numbers (if they are over 1,000 they tend to get fuzzy for me). To put this in perspective, I read an estimate that if  all the telecommunication data in the United States was stored digitally for one year, it would take about 9.25 Exabytes of data.1

Anyways, now that I’m done geeking out, let’s get back to the situation at hand. Since this theoretically limit will never be achieved (at least by anyone that is reading this blog for practical purposes), what is the limiting factor? Well, your Operating System can be the limit. In this modern day and age, if you are running Civil 3D and aren’t running Windows 7, you should be shot. I can already hear you, “But IT won’t support Windows 7!” Well, THEY should be shot then. So, what version of Windows 7 are you running? THIS web page lists the different versions of Windows and the different amounts of RAM they will support. It’s put together nicely and is easy to follow. The Home versions of Windows 7 64-bit are limited to 2, 8, or 16 gigs of RAM whereas the professional and greater versions allow 192 gigs.

Now, don’t go out and buy 100 gigs of RAM just yet as there are other limits to the amount of RAM you can use. Currently (if you aren’t using a Home version), what limits your RAM is your hardware, aka motherboard. Most modern motherboards can’t handle that much RAM. I did a quick search of TigerDirect and NewEgg and found that most of the high end motherboards will support up to 24 gigs of RAM.

I’m sure there will come a day and age when we look back and think to ourselves, “Remember when we use to buy RAM in Gigabytes?” and then chuckle a little bit. Ah, can’t wait to not be in the good old days anymore!