when caching is enabled, my EDMA performance decreases

hi every one.
according to the dm640's EDMA text reference(spru234c) EDMA's urgent priority is used for caching transfers when caching is active. I have a software with interface with E1 stream thorogh MCBSP which its events are serviced by EDMA in high priority. when Cache is not enabled, edma and my whole software works properly. but when cache is enabled it seems that EDMA's performance decreases significantly and misses some of MCBSP's events. in this case I have to set MCBSP's EDMA events to urgent level to make EDMA work better. my MCBSP events are generated every 500 micro second to EDMA.
Is this really normal? when working in caching-enabled mode, should I normally expect EDMA to miss events? what can I do to approve my EDMA's performance?
Thanx for considering my problem.

_____________________________________ Start a New Thread