PC Hardware in a Nutshell, 3rd Edition [Electronic resources] نسخه متنی

15.6 Troubleshooting Video Adapter Problems

If you experience video problems,
first check the obvious thingsthat the monitor has power and
is connected properly to the adapter, that no one has changed
settings on the monitor, and so on. If you have another monitor
handy, try connecting it to the problem system to eliminate the
monitor as a possible cause.

Once you eliminate those possible causes, the next consideration is
whether you've made any recent changes to your video
hardware, software, or configuration. If so, that is a likely cause.
Sometimes, problems caused by such a change don't
manifest immediately. We have, for example, seen an updated driver
function perfectly until one particular program was loaded or another
piece of hardware was installed, which caused the system to crash and
burn horribly.

That means the next step is to change video drivers. If a later
driver is available, download and install it. If no later driver is
available, try reinstalling the current driver. If problems manifest
soon after installing an updated driver, try re-installing the older
driver.

Once they are installed and running properly, video adapters seldom
fail, short of something like a lightning strike or abusing the
adapter by overclocking it. In our more than 20 years of experience
with hundreds of systems, we remember only a few instances when a
functioning video adapter just died. Hardware failures are more
likely today, not because newer video adapters are inferior to their
parents, but because they're now pushed harder.
High-end video adapters nowadays come with at least a heatsink for
the graphics processor, and it's not unusual to see
a video adapter on a gamer's system with a fan or
even a Peltier cooler installed. If you install a high-performance
adapter, make absolutely certain that the fan, if any, has power, and
that there is free airflow to the heatsink. Many video problems on
systems so equipped are due to simple overheating.

Here are some specific problems you may encounter, and how to remedy
them:

Windows is using the standard VGA driver. If Windows 9X cannot detect
the display adapter type when it is installed, it installs the
vanilla VGA driver. Windows may have been installed or reinstalled
improperly, or the display adapter may have been deleted in the
Device Manager, and Windows did not successfully detect the video
adapter the last time it was restarted. If the Color palette has
options higher than 16, but the desktop area is fixed at 640x480, the
monitor type may be incorrect or missing. To solve this problem,
install the correct drivers for the video adapter and/or monitor.

This problem is also caused by incorrect video drivers or
configuration errors. The startup screen is a low-resolution image
that is displayed at standard VGA settings. To solve the problem,
restart the system in Safe Mode, and reinstall or reconfigure the
drivers for the video adapter and/or monitor.

One likely cause is a corrupted ShellIconCache file, a problem that
occurs frequently on systems running IE4 and TweakUI, but is by no
means limited to those environments. To solve this problem under
Windows 9X or NT, uninstall TweakUI (if it is installed), then delete
or rename ShellIconCache (in the Windows directory) and restart the
system, which automatically rebuilds the ShellIconCache file.
Alternatively, view Display Properties Appearance.
In the Item drop-down list, select Icon. Use the Size spinner to
change the icon size one step up or down and click Apply to save the
change. Change the icon size back to its original value and click OK
to save the change and exit the dialog. This process forces Windows
to rebuild ShellIconCache. Icon display problems also occur sometimes
on Windows NT 4 systems running early builds, a situation that is
easily solved by installing the latest service pack. Finally, we have
seen this behavior caused on one system by overheating. In that case,
the icons displayed normally for some time after the system was
started, but turned into black boxes after the system had been
running for some time. Cleaning the dust out of the system and
installing a supplemental cooling fan made the problem go away, and
it has never returned.

These screen artifacts may appear only when using certain
combinations of resolution and color depth, and are not affected by
mouse movement or by running a different application. They may be
persistent or may appear and disappear seemingly at random. This
problem is a result of malfunctioning video memory. Possible causes
include: upgrading an adapter with slow or mismatched memory;
overclocking an adapter, improperly seated memory modules or corroded
connectors; and the video adapter not being fully seated. If you are
overclocking the adapter, stop doing so and see if the problem goes
away. If the adapter is out of warranty and at least a year or two
old, consider replacing it. Even inexpensive current adapters greatly
outperform anything of that vintage. If you decide to troubleshoot
the problem, observe antistatic precautions. Remove and reseat the
adapter in its original slot. If it is a PCI adapter, try moving it
to another slot. Use your thumb to press gently on each chip or
memory module to ensure it is fully seated. If the adapter uses
memory modules, remove and reseat each of them, although this may be
impractical if the modules require special tools. Use rubbing alcohol
or a commercial contact cleaning product to clean accessible
connectors and slots, both for memory and for the adapter itself. If
you have recently installed a memory upgrade on the adapter, remove
it temporarily to see if the problem disappears.

If this occurs when you build or upgrade a system, the most likely
cause is incorrect video drivers. Download and install the most
recent stable video drivers for your adapter. If it occurs on a
system that had been working correctly, there are several possible
causes. If text entered in an application appears in a strange font,
but menus and other system fonts are correct, use preferences or
options within the application to choose another font. If menus are
scrambled only within one application, uninstall and then reinstall
that application. If the problem occurs in multiple applications and
system applets, system font files may have been corrupted or replaced
with older, incompatible versions. The easiest cure is to reinstall
the operating system, using its repair option. If you run Windows 9X,
the hardware acceleration setting may be too high. Decrease it, as
described in the preceding section on Windows 98/Me. Although this
problem usually is obvious when the system is first brought up, we
have seen it occur on a system that had been running perfectly at the
highest setting. In that case, installing a DVD drive broke the
system. As it turned out, reducing hardware acceleration by one level
allowed the video card and DVD drive to coexist, but we ultimately
replaced the video card with a later model that would run with full
hardware acceleration.

Windows NT does not support AGP, but treats an AGP card as a PCI
card. If the motherboard maps the IRQ assigned to the AGP slot to the
same IRQ used by the first PCI slot, installing the AGP card creates
an IRQ conflict. Move the affected PCI card to a different slot, or
use BIOS Setup to remap IRQ assignments.

This is often caused by insufficient system resources (such as a slow
processor, aging video adapter, or inadequate memory), by having too
many other programs running, or by attempting to display DVD video at
too high a resolution and/or color depth. If you use software MPEG
decoding, instead of replacing the processor, consider upgrading to a
video card that has DVD hardware support. If the DVD drive is ATAPI,
configure it for DMA mode rather than PIO mode (see Chapter 12).
Finally, Windows 9X IRQ Steering may configure the video card to
share an IRQ with another card, such as a network card. Use the
Device Manager to check IRQ assignments and verify that the video
card is not sharing its IRQ. If it is, relocate the PCI card to a
different slot.

This is an artifact of how some DVD MPEG decoder cards function,
mapping the DVD video to one particular overlay color. As a temporary
fix, connect the monitor directly to the video card except when you
are displaying DVD video. The only real fix is to remove the DVD
decoder and the current video card, and install a newer video card
that provides hardware DVD acceleration.