A cache controller operable to control a cache comprising cache lines, each being
operable to store data words and validity information indicating that all data
words within that cache line are valid. The cache controller comprises a linefill
mechanism operable to write data words to a cache line, to provide an indication
when each of the data words has been written to the cache and to set the validity
information when all data words in the cache line have been written; and a data
word accessing mechanism, responsive to a request to access a data word during
a linefill operation prior to the validity information being set, to determine
from the indication provided by the linefill mechanism whether the data word to
be accessed has already been written during the linefill operation and, if so,
to provide a signal indicating that the data word is accessible.
