Windows 7 - Win 7 Legacy driver using wrong gap count

Asked By Paul on 10-Aug-12 12:24 PM
I have a Win7x64 systems that is under-performing from a 1394 standpoint.  =
That is, the device is working fine until I start to push the bus throughpu=
t close to it capabilities, then data loss occurs (buffer overflows).  If I=
try a different 1394a adapter on the same system, it works fine.  I used a=
1394 bus analyzer, and I see that my problem seems to be rooted in the gap=
count that the 1394 bus controller is choosing; it=92s using the maximum (=
and default) value of 63, even though it=92s a point-to-point connection (w=
ith a reasonable length cable).  The working adapter will set the gap count=
to 10 or 11.  The bus is not capable of chaieving the throughput I need wi=
th this very 'relaxed' setting for the gap count

In both cases, I=92m using the legacy driver (as this is the one qualified =
for this system).=20

Is there isome way I can configure this system to use a shorter gap count?  =
I could use a SET_LOCAL_HOST_PROPERTIES_GAP_COUNT, but that will only set t=
he lower bound to allow long cables =96 I would need an upper bound limit t=
o ensure the necessary bus performance.  I also found this reference=20


which sets the StaticGapCount/GapCountMethod registry entries, but that did=
not work =96 the host controller still uses a gap count of 63.

Any ideas?