Infer BRAMs with all bits used for buffering

Hey,

Have someone managed to infer a BRAM of maximum width (9, 18, 36 etc) and get the expected resource utilization? When infering a 36x512 buffer, xst uses BRAMS but for 32x512, only one is used. Does this have anything to do with the parity bits? How do I specify that I want to use them for buffering as well?

Coregen gives what I'm expecting but I would like to infer the buffer of a number of reasons (to keep the design consistent, to speed up simulations...).

Someone have a solution for this?

Thanks,
Martin

martin.wahlstedt