Intel 815 manual Initialization Registers, Standard VGA Registers, Smram Registers

Intel® 815 Chipset: Graphics Controller PRM, Rev 1.0

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7.Initialization Registers

To function, all registers described in this section must be programmed for the Intel® 815 chipset family of products. The default states of these registers, with the exception of registers that deal with extended modes or performance enhancements, will prevent the Intel® 815 chipset family products from booting.

Note: The registers in this document are normally programmed by the video BIOS.

These registers also may be documented in other sections of this document.

7.1.Standard VGA Registers

All VGA registers are in standard locations and initialized by means of standard procedures. This section will document all nonstandard registers that are needed for initialization of the Intel® 815 chipset.

7.2.SMRAM Registers

The SMRAM register is in the chipset’s PCI configuration space (Device 0). Since this register is not documented anywhere else, the entire register description is provided here.

7.2.1.SMRAM—System Management RAM Control Register (Device 0)

Address Offset:	70h
Default Value:	00h
Access:	Read/Write, Read Only
Size:	8 bits

The SMRAM register controls how accesses to Compatible and Extended SMRAM spaces are treated, and how much (if any) memory is “Stolen” from the System to support both SMRAM and Graphics Local Memory needs.

7	6	5	4	3	2	1	0
Graphics Mode Select		Upper SMM Select		Lower SMM Select		SMM	E_SMRA
						Space	M_ERR
						Locked

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