[请教]BIOS地址映射?

暴雪

原512K的ROM，现换了一个1M的ROM，windows下在 0xFFF0 0000~0xFFF7 FFFF 可以看到追加的512K的内容。
但在启动计算机时(BIOS没有初始化计算机），无法访问追加的512K的ROM。
(可以访问原512K的ROM 0xFFF8 0000~0xFFFF FFFF)

我的计算机用的是intel的ICH7南桥。
在手册上
9 m4 P& P& Y7 j+ WFWH_SEL2—Firmware Hub Select 2 Register (LPC I/F—D31:F0)
FWH_70_IDSEL — R/W. IDSEL for two, 1-M Firmware Hub memory ranges.
! W  i' N9 A5 X1 k7 U6 e& H4 T+ tThe IDSEL programmed in this field addresses the following memory ranges:
FF70 0000h – FF7F FFFFh
/ w( M. U5 ^$ X* q7 `" O7 g7 yFF30 0000h – FF3F FFFFh
在这里 IDSEL 如何理解。
FWH_DEC_EN1—Firmware Hub Decode Enable Register
(LPC I/F—D31:F0)
' R  r2 R) O/ m, QFWH_70_EN — R/W. Enables decoding two 1-M Firmware Hub memory ranges.
3 s4 T, Z. p, k& N4 t  R  R0 = Disable.
1 = Enable the following ranges for the Firmware Hub
' M% E( @$ o2 M* [( Z( aFF70 0000h – FF7F FFFFh
FF30 0000h – FF3F FFFFh
除了上面的数据区域，还有其它的数据区域控制ROM到内存地址的映射吗？
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/ K" L4 n' ^8 y0 L, l谢谢大家了！！！

xtdumpling

IDSEL是LPC spec的一个信号(Device Select),
This one clock field is used to indicate which of multiple Firmware components is being selected.
2 }: T' e/ V) Y0 n8 Q5 pThe four bits transmitted over AD[3:0] during this clock are compared with values strapped onto
pins on the Firmware component. If there is a match, the Firmware component will continue to
decode the cycle to determine which bytes are requested on a read or which bytes to update on a
6 `% {9 L) w# A' Q: z6 o, I- p$ ewrite. If there isn’t a match, the Firmware component may discard the rest of the cycle and go into
3 S" h3 L+ E5 z( ]2 I8 w( ]! F, ?a standby power state.
) T4 O* A6 }, \9 M8 V
7 Z, d& K% Q! [/ L# N! }详见LPC spec:
http://www.intel.com/design/chipsets/industry/25128901.pdf
- b" O! Z+ u# u0 X* X
在ICH 7 中似乎就这几个吧(FWH_SEL1,FWH_SEL2,FWH_DEC_EN1,BIOS_CNTL),据我现在知道的.