Intel 815 manual Graphics Driver Startup

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® 815 chipset is in GFX mode, this algorithm gives preference to the internal graphics controller over a 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):

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:

•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.

The following Video BIOS initialization steps only apply if the GMCH is in “Internal Graphics Mode” (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 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:

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).

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.)

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