A graphic accelerator interface device for a computer is provided. The
accelerator has a host data path that includes a plurality of comparators,
each assigned to permit os/application access to a different "surface"
which is defined by an address range corresponding to a block of data in a
frame buffer. Unlike the prior art, an access flag register is associated
with the host data path such that each surface assigned to a comparator
has associated read and write flags. Whenever a read or a write occurs to
one of the assigned surfaces via the host data path, the corresponding
flag is set. Preferably, for os/application access, the surfaces contain
data in an untiled format which the graphic accelerator uses in a tiled
format. The invention affords more efficient, i.e. faster, processing,
since the graphics driver can use prior tiled format data, if the write
flag is clear, instead of processing the untiled data stored in an
assigned surface into a useable tiled format which is only needed if the
untiled data has been changed, i.e. indicted by the write flag being set.
