PIIX datasheet(37/122 Pages) INTEL

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82371FB (PIIX) AND 82371SB (PIIX3)

Bit

Description

ISA/DMA Lower BIOS Forwarding Enable. 1=Enable (forwarded to PCI, if XBCS Register

bit 6=0); 0=Disable (contained to ISA). Note that If the XBCS Register bit 6=1, ISA/DMA

accesses in this region are always contained to ISA.

PIIX: Reserved

PIIX3: A,B Segment Forwarding Enable. 1=Enable (forward to PCI), 0 = Disable (default,

contain to ISA). When enabled, this bit allows ISA Master and DMA memory accesses to

A0000h

−BFFFFh range to be forwarded to PCI. When disabled, these accesses are

contained to ISA.

ISA/DMA 512–640-Kbyte Region Forwarding Enable. 1=Enable (forwarded to PCI);

0=Disable (contained to ISA).

Reserved

2.2.12.

MSTAT—MISCELLANEOUS STATUS REGISTER (Function 0)

Address Offset:

6B–6Ah

Default Value:

Undefined

Attribute:

PIIX: Read/Write (bits [1:0] are read only)

PIIX3: Read/Write Clear(bits 1 is read only)

This register provides miscellaneous status and control functions.

Bit

Description

PIIX: Reserved.

PIIX3: SERR# Generation Due To Delayed Transaction

R/WC. PIIX3 sets this bit to a 1

when it generates SERR# due to a delayed transaction. Software sets this bit to a 0 by writing

a 1 to it.

14:8

Reserved.

PIIX: Reserved

PIIX3: NB Retry Enable (NBRE)--R/W, 1=Enable, 0 = Disable (default). This bit, when

enabled, causes the PIIX3 to retry, without initiating a delayed transaction, CPU initiated,

non-LOCK#, PCI cycles. No delayed transactions to PIIX3 may currently be pending and

passive release must be active. Delayed Transactions and Passive Release must both be

enabled via the DLC Register (function 0, offset 82h). When disabled, the PIIX3 accepts

these cycles as normal, which may include retry with initiation of a delayed transaction.

PIIX Scheda tecnica(PDF) 37 Page - Intel Corporation