capacity of seda/vm with multipleConsumers=true?

[Keith Freeman]

My understanding is that using multipleConsumers=true on a seda:/vm: 
endpoint makes it behave more-or-less like a JMS topic.  Does it then 
have a capacity at which producers will throw/block (e.g. if there are 
no consumers), or does it behave more like an LRU ring buffer, writing 
new values on top of oldest ones?  Or something else?

The component page doesn't give much detail about this case.