AMD Geode™ LX Processors Data Book 281
Display Controller 33234H
6.5.1 GUI Functional Overview
6.5.1.1 Display Mode Suppor t
The display modes listed in Table 6-32 are supported by
the GUI block. 32- and 24-bpp display support is provided
across all resolutions. The Dot Clock source (DOTCLK) is
provided by a PLL. Available memory bandwidth deter-
mines the resolutions and color depths that will function
without display tearing. Memory controller configuration,
GLIU frequency, and other demands on the memory con-
troller set the available bandwidth. The GLIU frequency
determines the memory controller frequency. Other
demands on the memory controller such as the CPU and
bus masters affect on available bandwidth are difficult to
predict. Use of the video overlay feature additionally
decreases the bandwidth available for screen refresh.
The Minimum GLIU Frequency criteria listed in Table 6-32
must be met for quality operation of the display. This fre-
quency provides sufficient memory bandwidth for the mem-
ory controller to maintain reliable display refresh under all
operating conditions, including the video overlay. As a gen-
eral rule, Table 6-32 indicates what the minimum relation-
ship of DOTCLK to GLIU frequency should be at the
various color depths.
Bandwidth requirements for the VGA engine are not listed
in this table. Most graphics modes require the same band-
width as comparable 8-bpp display modes listed in Table 6-
32. Text modes generally require higher bandwidth. Sup-
ported text modes require a GLIU clock frequency of 100
MHz or more to obtain the necessary memory bandwidth.
Table 6-32. Display Modes
Resolution Color Depth (bpp) Refresh Rate (Hz) Dot Clock (MHz) Min. GLIU Frequency (MHz)
640 x 480 8, 16, or 24/32 60 25.175 75
8, 16, or 24/32 70 28.560 75
8, 16, or 24/32 72 31.500 75
8, 16, or 24/32 75 31.500 75
8, 16, or 24/32 85 36.000 75
8, 16, or 24/32 90 37.889 400
8, 16, or 24/32 100 43.163 400
800 x 600 8, 16, or 24/32 60 40.000 75
8, 16, or 24/32 70 45.720 75
8, 16, or 24/32 72 49.500 75
8, 16, or 24/32 75 49.500 75
8, 16, or 24/32 85 56.250 75
8, 16, or 24/32 90 60.065 400
8, 16, or 24/32 100 68.179 400
1024 x 768 8, 16 or 24/32 60 65.000 75
8, 16, or 24/32 70 75.000 100
8, 16, or 24/32 72 78.750 100
8, 16, or 24/32 75 78.750 100
8, 16, or 24/32 85 94.500 100
8, 16, or 24/32 90 100.187 400
8, 16, or 24/32 100 113.310 400
1152x864 8, 16, or 24/32 60 81.600 100
8, 16, or 24/32 70 97.520 100
8, 16, or 24/32 72 101.420 200
8, 16, or 24/32 75 108.000 200
8, 16, or 24/32 85 119.650 200
8, 16, or 24/32 90 129.600 400
8, 16, or 24/32 100 144.000 400