Holy cow, I wrote a book!
a comment to one of my earlier entries,
someone mentioned a driver that bluescreened under normal
conditions, but once you enabled the Driver Verifier
(to try to catch the driver doing whatever bad thing it was doing),
the problem went away.
Another commenter bemoaned that WHQL certification didn't
seem to improve the quality of the drivers.
Video drivers will do anything to outdo their competition. Everybody knows that
they cheat benchmarks, for example.
I remember one driver that ran the DirectX "3D Tunnel" demonstration program
extremely fast, demonstrating how totally awesome their video card is.
Except that if you renamed TUNNEL.EXE to FUNNEL.EXE, it ran slow again.
There was another one that checked if you were printing a specific
string used by a popular benchmark program.
If so, then it only drew the string a quarter of the time and merely
returned without doing anything the other three quarters of the time.
Bingo! Their benchmark numbers just quadrupled.
Anyway, similar shenanigans are not unheard of when submitting a
WHQL for certification. Some unscrupulous drivers will
detect that they are being run by WHQL and disable various
features so they pass certification. Of course, they also run
dog slow in the WHQL lab, but that's okay, because WHQL is
interested in whether the driver contains any bugs, not
whether the driver has the fastest triangle fill rate in the industry.
The most common cheat I've seen is drivers which check
for a secret "Enable Dubious Optimizations" switch in the
registry or some other place external to the driver itself. They take
the driver and put it in an installer which does not turn the
switch on and submit it to WHQL. When WHQL runs
the driver through all its tests, the driver is running in
"safe but slow" mode and passes certification with
The vendor then takes that driver (now with the WHQL stamp
of approval) and puts it inside an installer that enables the
secret "Enable Dubious Optimizations" switch. Now the
driver sees the switch enabled and performs all sorts of
dubious optimizations, none of which were tested by WHQL.