Newbie question about clusters and memory.

Is there a way using a cluster (or any other Linux feature/technology) where I can link up a bunch of PCs such that an app thinks it has more memory than available on just one local machine?

For example, we have multiple surplus PCs with 512MB RAM (which is the max that that hw supports). Is there a way to cluster or link them up in some way such that an app would think that it has more than the 512MB RAM available, say 1GB or anything else?

I am fully aware that the speed in such a hypothetical situation would be less than ideal, but speed is not the primary concern at the moment. The primary concern is available memory.

I (think I) know how to link up machines such that disk space on several PCs could be available to an app such that the disk space for the app exceeds the available space on the local machine. But is there a way to do this with memory... using cluster or any other Linux feature or technology?

Thanks for your replies (and don't beat me up too much if this is an insane question, I'm just a newbie :-) ).