2 - Refresh Rates
the Refresh Rate drop down there are two common
settings, Adapter Default and Optimal. Depending
on the drivers used for the video card and monitor,
there may be individual refresh rate settings
(i.e. 60Hz, 70Hz, 72Hz, etc.) as well. However,
if you choose one of the individual refresh
rates listed, it will only be good for that
resolution. If you change resolutions (common
if you are a gamer), then the refresh rate will
generally switch to 60Hz for that resolution
and that isn't a good thing. When the game is
exited, the prior resolution and refresh rate
should be restored. But is there an alternative?
That is were the "Optimal" refresh
rate comes into play. Theoretically, the
"Optimal" setting should set the highest
recommended refresh for a given resolution.
I say theoretically because, in practice that
rarely happens. I've seen many newsgroup
posts of people complaining that no matter what
resolution they are using, the "Optimal"
setting leaves them at 75Hz and that has been
my experience as well. So what gives?
My monitor can do up to 100Hz at 1152x864, why
is it only doing 75Hz? I decided to contact
nVidia and get an explanation. Peggy Seltz,
Software Manager Windows 2D/Video Development
was kind enough to educate me on the fine points
of refresh rates.
refresh rates are very confusing because it
means different things to different vendors.
Most people assume this is the maximum refresh
rate that a monitor can support, but that
is not always the case. Many system vendors
have us cap the optimal refresh rates so they
don't damage their customers' monitors. The
problem we see from the driver perspective
is we don't always have the information that
we need. Sometimes we don't have a monitor
.INF, and when we do, the information is not
always reliable. The same thing goes for a
monitor EDID. Even when
we have enough information (and assume it
is reliable) many system vendors don't want
to risk damaging any monitors so they will
cap the optimal refresh rate to a fixed value,
for example, 75Hz.
that's why so many of us are stuck on 75Hz maximum
"Optimal" refresh rate. She goes on
can set a specific refresh rate in display
properties (advanced tab). This lists all
of the refresh rates that Windows has determined
are safe for your monitor based on the information
available to Windows (the driver .INF, the
monitor .INF and the EDID). When setting a
refresh rate, if the driver doesn't have enough
info, it will use the information that it
does have and make an intelligent but safe
guess, which could be lower than the true
maximum refresh rate supported by your monitor.
We really go to great lengths to try to get
this all correct for all cases, but as you
can imagine, there are always some corner
cases - for example an incorrect monitor .INF
installed for a monitor, or EDID info that
is not valid.
people complain that they can't get above 640x480
after installing new drivers. Nine times
out of ten, it's because the monitor wasn't
detected properly. When they choose the
right monitor, then everything works again.
It is possible for a new monitor to work using
a different monitor's drivers, however the new
monitor's capabilities won't be properly recognized.
possibility is that Windows has determined
(with the information available) that 75Hz
is the max refresh that your monitor is capable
of at this resolution. If you don't have a
choice higher than 75Hz in display properties,
then this is the case.
if you choose a less than standard resolution
like 1152x864 with a refresh rate above 75Hz,
you no longer are using VESA DMT monitor timings,
but rather GTF timings. The only DMT
timing defined for 1152x864 is for 75Hz refresh.
If you chose the monitor's maiximum refresh
rate at any resolution, would it use GTF timings?
depends on the refresh rates that your monitor
is capable of. For 1152x864, if the driver
determines that your monitor is capable of
refresh rates other than 75Hz, the driver
will use GTF timings for the other refresh
rates. For the 1152x864 resolution, the only
VESA DMT monitor timings that are defined
are for 75Hz refresh rate.
there you have it. Most monitor manufacturers,
while advertising ultra-high refresh rates,
are more apt to error on the side of caution.
Finally, this closing thought...
manufacturers are actually starting to do
a good job of improving the EDID information
and are giving us monitor range limits so
we can determine the timings based on these
values instead of fixed refresh rates.
after choosing the "Optimal" setting,
you may want to see what value was selected.
Most monitors offer the ability to check the
refresh rate via the OSD (OnScreen Display).
On my old Panasonic monitor, just hitting the
number "2" button would show the refresh
rate. On my new Viewsonic monitor, it's called
"Viewmeter". The value you are looking
for is FV or Vertical refresh rate.
again to Peggy and the fine folks at nVidia
for taking some time out of their busy schedules
to drop a few pearls of wisdom on me. As always,
feedback on this is welcomed. The followup to
this article also features refresh rates and
the relationship with VSYNC. Click
here for that article.
Since Windows XP came out, much of this article
no longer applies. However, Win XP (and Windows
2000) bring their own problems with Refresh