eDirectory 88 SP3 shipped with a 64-bit version of eDirectory on Linux. eDirectory 884 was also available as 64-bit on the 64-bit OES Linux. 64-bit eDirectory was a cross platform release of 88 SP5.
There were lot of questions for us to explain the benefits of 64-bit eDirectory. We have tried to evaluate the 32-bit & 64-bit eDir in various scenarios. The document at http://www.novell.com/docrep/2009/10/64bit-edirectory-white-paper_Sept2009_en.pdf
should help in this regards.
Disclaimer: As with everything else at NetIQ Cool Solutions, this content is definitely not supported by NetIQ, so Customer Support will not be able to help you if it has any adverse effect on your environment. It just worked for at least one person, and perhaps it will be useful for you too. Be sure to test in a non-production environment.