IORD IOWR macros vs. memory access to peripherals

Volatile doesn't instruct the compiler to avoid the cache. It prevents the compiler from optimizing read/writes to the variable, ensuring that all read/write operations are indeed done by the compiled code. But it will still use the cache.

The only ways to bypass the cache are the IORD/IOWR macros, and to map the accessed memory in uncached areas using alt_remap_uncached(), or the special uncached malloc functions.

Edit: Sorry BillA, this is in fact exactly what you said... I should definitely NOT answer anything before my morning coffee...