参数资料
型号: IBM21P100BGB
元件分类: 总线控制器
英文描述: PCI BUS CONTROLLER, PBGA304
封装: 31 X 31 MM, HEAT SINK, PLASTIC, BGA-304
文件页数: 104/140页
文件大小: 2032K
代理商: IBM21P100BGB
IBM21P100BGB
IBM 133 PCI-X Bridge R1.1
Configuration Registers
Page 58 of 131
ppb11_pcix_regs.fm.03
July 9, 2001
5.2.5.2 Secondary Data Buffering Control Register
The Secondary Data Buffering Control register provides controls for memory read transactions that are initi-
ated on the secondary interface.
Address Offset
x‘42’
Access
See individual bit fields.
Reset Value
x‘0020’
Res
e
rv
ed
M
a
ximum
M
emo
ry
R
ead
B
y
te
Count
E
nable
R
elaxe
d
O
rdering
S
e
condary
S
pecial
D
elay
ed
Read
Mod
e
S
e
condary
R
ead
Pr
ef
et
ch
bi
ts
S
e
condary
R
ead
Line
P
ref
et
c
h
bit
s
S
e
condary
R
ead
Mu
lt
ipl
e
P
ref
et
ch
bit
s
Res
e
rv
ed
15 14 13 12 11 10
9
876543210
Bit(s)
Access
Field Name and Description
15
RO
Reserved
14:12
RW
Maximum Memory Read Byte Count
These bits set the maximum byte count used by the bridge when generating read requests on the primary
bus in response to a memory read operation initiated on the secondary bus (when the secondary bus is in
PCI mode). Device drivers must not modify these bits without considering the impact on the rest of the sys-
tem. These bits only have an effect if the prefetch mode bits for the PCI read command in use (bits (9:8),
(7:6), or (5:4) below) are set to “full prefetch”. The most recent value of this register is used each time the
bridge makes a new read request. The bits have the following meaning:
000
default to 512 bytes
001
128 bytes
010
256 bytes
011
512 bytes
100
1024 bytes
101
2048 bytes
110
4096 bytes
111
default to 512 bytes
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