Intel G645 BX80623G645 User Manual

16

Datasheet, Volume 2

• Device 6, Function 0

— MBASE/MLIMIT – PCI Express port non-prefetchable memory access window. 
— PMBASE/PMLIMIT – PCI Express port prefetchable memory access window.
— PMUBASE/PMULIMIT – PCI Express port upper prefetchable memory access 

window

— IOBASE/IOLIMIT – PCI Express port I/O access window.

• Device 2, Function 0 

— IOBAR – I/O access window for internal graphics. Through this window 

address/data register pair, using I/O semantics, the IGD and internal graphics 

instruction port registers can be accessed. Note, this allows accessing the same 

registers as GTTMMADR. The IOBAR can be used to issue writes to the 

GTTMMADR or the GTT table.

— GMADR – Internal graphics translation window (128 MB, 256 MB, 512 MB 

window). 

— GTTMMADR – This register requests a 4 MB allocation for combined Graphics 

Translation Table Modification Range and Memory Mapped Range. GTTADR will 

be at GTTMMADR + 2 MB while the MMIO base address will be the same as 

GTTMMADR.

The rules for the above programmable ranges are: 

1. For security reasons, the processor will now positively decode (FFE0_0000h to 

FFFF_FFFFh) to DMI. This ensures the boot vector and BIOS execute off PCH.

2. ALL of these ranges MUST be unique and NON-OVERLAPPING. It is the BIOS or 

system designers' responsibility to limit memory population so that adequate PCI, 
PCI Express, High BIOS, PCI Express Memory Mapped space, and APIC memory 
space can be allocated.

3. In the case of overlapping ranges with memory, the memory decode will be given 

priority. This is a Intel TXT requirement. It is necessary to get Intel TXT protection 
checks, avoiding potential attacks.

4. There are NO Hardware Interlocks to prevent problems in the case of overlapping 

ranges. 

5. Accesses to overlapped ranges may produce indeterminate results.
6. Software must not access B0/D0/F0 32-bit memory-mapped registers with 

requests that cross a DW boundary.

Figure 2-1

 represents system memory address map in a simplified form.