Disabling cache for some data

[Claudio Scordino]

Hi,

   I have to write a dummy testing program which continuously reads 2 bytes on 
RAM, fills a buffer, and then sends all the data through the Ethernet interface.
It's used just to evaluate the maximum throughput that I would have reading from 
memory and sending to Ethernet.

However, If I read always the same data, the processor uses the cache and does 
not perform a memory read.

My question is: how can I tell gcc to not cache such data ?

Many thanks for any help and suggestion,

         Claudio