Intel 815 Manuel D’Utilisation
Intel® 815 Chipset: Graphics Controller PRM, Rev 1.0
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14. During PCI enumeration, the system BIOS will identify and initialize the primary display device.
The selection of the primary display device is typically OEM dependent. An OEM may use a
BIOS setup question to allow the system user to select the primary display device. Intel
recommends the system BIOS to give preference to the higher performance display device when
performing an “auto-selection” of the primary display device. If the GMCH is in AGP mode, this
algorithm gives preference to the AGP graphics device over a PCI VGA device. If the Intel
BIOS setup question to allow the system user to select the primary display device. Intel
recommends the system BIOS to give preference to the higher performance display device when
performing an “auto-selection” of the primary display device. If the GMCH is in AGP mode, this
algorithm gives preference to the AGP graphics device over a PCI VGA device. If the Intel
®
815
chipset is in GFX mode, this algorithm gives preference to the internal graphics controller over a
PCI VGA device.
PCI VGA device.
15. Once the primary display device has been initialized, system BIOS will pass control to the Video
Option ROM corresponding to that display device.
16. If and only if the GMCH is in GFX Mode (APCONT[0] = 1), the Video Option ROM will perform
initialization routines described below.
17. System BIOS then completes the system test including testing the rest of main memory.
The following System BIOS initialization steps only apply if the GMCH is in “Internal Graphics Mode”
(Not AGP):
(Not AGP):
1. System BIOS determines if a GPA card (i.e., Local Memory) is present. This is accomplished the
same as on the Intel
®
810 chipset: Enable Local Memory via the DRT, DRAMCL, and DRAMCH
(offsets 3000-3002h) and attempt to write and readback a location in Local Memory. If the
readback returns the same data that was written previously, then it can be assumed that Local
Memory is present. If a GPA card is present, the following additional steps take place:
readback returns the same data that was written previously, then it can be assumed that Local
Memory is present. If a GPA card is present, the following additional steps take place:
• System BIOS configures the Local Memory Timing Options via the DRAMCL register at
Device 2 Memory Mapped Register offset 3001h. There is no Serial Presence Detect
mechanism available for the Local Memory / GPA Card interface, so the method used to
determine these timing options is entirely up to the OEM. One conservative option is to leave
the DRAMCL register with its default settings, which are the slowest available. Another
option is to enforce certain minimum timings on any GPA cards used by that OEM, and
program the DRAMCL with those minimums. While not recommended, it is also possible to
determine optimal timings empirically.
mechanism available for the Local Memory / GPA Card interface, so the method used to
determine these timing options is entirely up to the OEM. One conservative option is to leave
the DRAMCL register with its default settings, which are the slowest available. Another
option is to enforce certain minimum timings on any GPA cards used by that OEM, and
program the DRAMCL with those minimums. While not recommended, it is also possible to
determine optimal timings empirically.
The following Video BIOS initialization steps only apply if the GMCH is in “Internal Graphics Mode”
(Not AGP):
(Not AGP):
1. Video BIOS assumes a VGA monitor type, and initializes the 2D-display controller in text mode.
2. 2D Video BIOS should take care to keep track of BIOS changes due to chip version changes.
3. The 3D section should be software-reset and initialized. At this point, no 3D operation should be
2. 2D Video BIOS should take care to keep track of BIOS changes due to chip version changes.
3. The 3D section should be software-reset and initialized. At this point, no 3D operation should be
enabled, since this is done at the application/driver level.
2.3.1.3.1. Graphics Driver Startup
At this point the GMCH internal graphics controller has been configured and initialized. The remainder
of the graphics initialization occurs when the operating system calls the graphics driver. The graphics
driver must initialize the graphics component address re-mapping hardware. Tasks include:
of the graphics initialization occurs when the operating system calls the graphics driver. The graphics
driver must initialize the graphics component address re-mapping hardware. Tasks include:
1. Allocate memory for the GTT re-mapping table. Set the host memory type of graphics memory for
both physically local and system memory (i.e. enable Write Combining for local and non-local
memory: OS calls graphics driver which calls OS services for setting host memory type).
memory: OS calls graphics driver which calls OS services for setting host memory type).
2. Establish policy for limiting the amount of non-local video memory. The OS determines the
maximum amount of system memory that can be allocated as non-local video memory. The
graphics driver can make a guess on what is likely to be provided by the OS based on the same
information that the OS uses to make its decision. The graphics driver can query the OS to check
the type of memory surface allocation (i.e., system vs. local vs. non-local video memory.)
graphics driver can make a guess on what is likely to be provided by the OS based on the same
information that the OS uses to make its decision. The graphics driver can query the OS to check
the type of memory surface allocation (i.e., system vs. local vs. non-local video memory.)