So I have a section with 900 entries and I tried to just list them all on the page but Craft seems to choke after about 200 and will just not render any of them. Although I probably don't need to output all 900 it would be good to know what the issue is here?
Other than increasing the amount of memory available to PHP like Simon suggested, you can also lazy load the entries in batches using the limit and offset parameters. This would help keep the memory consumption down.
The extra entries would be triggered via infinite scrolling or treeview, etc. depending on how you're displaying them on the front-end.