Intel CONTROLLERS 413808 - Manual (Page 504)

Intel
®
413808 and 413812—System Controller (SC) and Internal Bus Bridge
Intel ® 413808 and 413812 I/O Controllers in TPER Mode
Developer’s Manual October 2007
504 Order Number: 317805-001US
7.5.5 Determining Block Sizes for Memory Windows
The memory window size can be determined by writing ones to the appropriate upper
bits of the limit register. The binary-weighted value of the first non-zero bit set in the
limit register indicates the size of the memory window. Table 338 describes the
relationship between limit register values and the byte sizes of the memory window.
As an example, assume that FFF0 0004H is written to the Bridge Window Limit Register
(BWLR). Scanning upwards starting at bit 12, bit 20 is the first one bit found. The
binary-weighted value of this bit is 1,048,576, indicating a 1 Mbyte of memory window.
When programming the Base and Limit Registers for a memory window, the Base
Address always needs to be aligned the size of the memory window set in a limit
register. For a 1 Mbyte memory window, only bit 20 through bit 31 of the base address
from the Bridge Base Address Register (BBAR) are relevant to the Bridge when
decoding Memory Window.
Warning:
Care must be exercised when modifying the Bridge Base (BBAR) and Limit (BWLR)
register pair during the time there is activity.
Warning:
Since the smallest bridge memory window is 4 KBytes, care must be exercised when
the bridge memory window is programmed to access memory-mapped registers that
are located on the north internal bus. The 4-KByte bridge window overlaps other south
internal bus memory-mapped registers. The user must not access the south internal
bus memory-mapped registers that overlap the bridge memory window until the bridge
memory window is re-mapped and does not overlap.
Table 338. Memory Block Size Limit Register Value
Limit Register Value
a
a. The smallest window supported is 4 Kbytes.
Size
(in Bytes)
Limit Register Value
Size
(in Bytes)
FFFFF000H 4K FF000000H 16M
FFFFE000H 8K FE000000H 32M
FFFFC000H 16K FC000000H 64M
FFFF8000H 32K F8000000H 128M
FFFF0000H 64K F0000000H 256M
FFFE0000H 128K E0000000H 512M
FFFC0000H 256K C0000000H 1G
FFF80000H 512K 80000000H 2G
FFF00000H 1 M
00000000H
Address
Window
Closed.
FFE00000H 2 M
FFC00000H 4 M
FF800000H 8 M