Specification Sheet

Processor Configuration Register Definitions and Address Ranges
34 Datasheet, Volume 2 of 2
2.4.1 DOS Range (0h – 9_FFFFh)
The DOS area is 640 KB (0000_0000h – 0009_FFFFh) in size and is always mapped to
the main memory.
2.4.2 Legacy Video Area / Compatible SMRAM Area (A_0000h –
B_FFFFh)
The same address region is used for both Legacy Video Area and Compatible SMRAM.
• Legacy Video Area: The legacy 128 KB VGA memory range, frame buffer, at
000A_0000h – 000B_FFFFh, can be mapped to Processor Graphics (Device 2), to
PCI Express (Device 1), and/or to the DMI Interface.
• Monochrome Adapter (MDA) Range: Legacy support requires the ability to have a
second graphics controller (monochrome) in the system. The monochrome adapter
may be mapped to Processor Graphics, PCI Express or DMI. Like the Legacy Video
Area, decode priority is given first to Processor Graphics, then to PCI Express, and
finally to DMI.
• Compatible SMRAM Address Range.
2.4.3 Legacy Video Area
The legacy 128 KB VGA memory range, frame buffer at 000A_0000h – 000B_FFFFh,
can be mapped to Processor Graphics (Device 2), to PCI Express (Device 1), and/or to
the DMI Interface.
2.4.4 Monochrome Adapter (MDA) Range
Legacy support requires the ability to have a second graphics controller (monochrome)
in the system. The monochrome adapter may be mapped to Processor Graphics, PCI
Express or DMI. Like the Legacy Video Area, decode priority is given first to Processor
Graphics, then to PCI Express, and finally to DMI.
2.4.5 Compatible SMRAM Address Range
When compatible SMM space is enabled, SMM-mode CBO accesses to this range route
to physical system DRAM at 00_000A_0000h – 00_000B_FFFFh.
Non-SMM mode CBO accesses to this range are considered to be to the Video Buffer
Area as described above. PCI Express and DMI originated cycles to SMM space are not
supported and are considered to be to the Video Buffer Area.
The processor always positively decodes internally mapped devices, namely the
Processor Graphics and PCI Express. Subsequent decoding of regions mapped to PCI
Express or the DMI Interface depends on the Legacy VGA configuration bits (VGA
Enable and MDAP). This region is also the default for SMM space.
2.4.6 Programmable Attribute Map (PAM) (C_0000h – F_FFFFh)
PAM is a legacy BIOS ROM area in MMIO. It is overlaid with DRAM and used as a faster
ROM storage area. It has a fixed base address (000C_0000h) and fix size of 256 KB.
The 13 sections from 768 KB to 1 MB comprise what is also known as the PAM Memory
Area. Each section has Read enable and Write enable attributes.