Specifications

158004.B00 29
ROM drives, and a Compact Flash socket to allow the use of Compact Flash cards in
place of mechanical hard disk drives.
Users will probably prefer to use the TP400’s IDE controller rather than the
TCDEVPLUS’s IDE controllers while using the TCDEVPLUS, since it is faster than
the TCDEVPLUS IDE controller. However, the TCDEVPLUS IDE controller may be
used. To do this the TCDEVPLUS IDE controller must be enabled at jumper area E4.
In addition, the IDE disk controllers on the TP400 must be disabled. This is achieved
using the Setup program (Advanced / I/O Device Configuration menu entries).
3.10 DISPLAY CONTROLLER
The TP400 provides a powerful graphics controller system. This display controller
logic is able to support CRT displays and active-matrix TFT colour LCDs. A PanelLink
driver is provided. Some EL and plasma panels may also work with the TP400. The
CRT and flat panel can operate simultaneously. CRT resolution is up to 1280 x 1024
and TFT resolution is up to 1024 x 768.
3.10.1 Overview
The graphics controller logic is one of the most interesting aspects of the Geode GX1
architecture. The logic is implemented in the Geode GX1 processor chip and the
CS5530A companion chip.
Some of the SDRAM is taken from the processor and allocated to the graphics
controller, using a technique referred to as UMA (unified memory architecture). Up to
4.5M bytes may be allocated to graphics. The BIOS allows an appropriate amount to
be reserved for graphics, in the Advanced / Advanced Chipset Control / Video
Resolution menu. The memory taken by each BIOS option is given in Table 4. This
memory is used for the display frame buffer, for the Geode’s unique display buffer
compression cache, for SMI processing and for video (MPEG and AVI) processing.
Unfortunately therefore, there is no direct correlation between the SDRAM allocated
and the display resolution and colour depth – this will be dependent on how each
display driver has been implemented. You may have to experiment with different
settings to get an optimum trade off between memory used and display resolution.
Table 4 shows guidelines which are adequate for Windows 95. (Note that there are
some anomalies here, which must be attributed to problems with the display driver).
BIOS SETTING SDRAM ALLOCATED TYPICAL DISPLAY RESOLUTION
LOW 1.5M bytes 1024 x 768 x 256 colours
MEDIUM 1.5M bytes 1024 x 768 x 256 colours
800x 600 x 65536 colours
HIGH 2.5M bytes 1024 x 768 x 65536 colours
1280 x 768 x 256 colours
SUPER 4.5M bytes 1024 x 768 x 65536 colours
1280 x 768 x 256 colours
TABLE 4 - SDRAM ALLOCATED TO DISPLAY CONTROLLER
In order to display an image on the screen, video data is read out of the graphics
area within the SRAM memory by the Geode GX1 processor, and sent to the