Intel D15343-003 manual Pcicmd PCI Command Register

Models: D15343-003

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Intel® 82854 Graphics Memory Controller Hub (GMCH)

4.8.3PCICMD – PCI Command Register

Address Offset:

04-05h

Default Value:

0006h

Access:

Read only, Read/Write

Size:

16 bits

Since GMCH Device #0 does not physically reside on PCI_A many of the bits are not implemented.

Bit

Descriptions

 

 

15:10

Reserved

 

 

9

Fast Back-to-Back Enable (FB2B): This bit controls whether or not the master can do fast back-

 

to-back Write. Since Device #0 is strictly a target, this bit is not implemented and is hardwired to

 

0. Writes to this bit position have no affect.

 

 

8

SERR Enable (SERRE): This bit is a global enable bit for Device #0 SERR messaging. The

 

GMCH does not have an SERR# signal, but communicates the SERR# condition by sending an

 

SERR message to the ICH4-M.

 

1 = Enable. GMCH is enabled to generate SERR messages over Hub interface for specific

 

Device #0 error conditions that are individually enabled in the ERRCMD register. The error status

 

is reported in the ERRSTS and PCISTS registers.

 

0 = SERR message is not generated by the GMCH for Device #0.

 

NOTE: This bit only controls SERR messaging for the Device #0. Device #1 has its own SERRE

 

bit to control error reporting for error conditions occurring on Device #1. The two control bits are

 

used in a logical OR manner to enable the SERR Hub interface message mechanism.

 

 

7

Address/Data Stepping Enable (ADSTEP): Address/data stepping is not implemented in the

 

GMCH, and this bit is hardwired to 0. Writes to this bit position have no effect.

 

 

6

Parity Error Enable (PERRE): PERR# is not implemented by GMCH and this bit is hardwired to

 

0. Writes to this bit position have no effect.

 

 

5

VGA Palette Snoop Enable (VGASNOOP): The GMCH does not implement this bit and it is

 

hardwired to a 0. Writes to this bit position have no effect.

 

 

4

Memory Write and Invalidate Enable (MWIE): The GMCH will never issue memory write and

 

invalidate commands. This bit is therefore hardwired to 0. Writes to this bit position will have no

 

effect.

 

 

3

Special Cycle Enable (SCE): The GMCH does not implement this bit and it is hardwired to a 0.

 

Writes to this bit position have no effect.

 

 

2

Bus Master Enable (BME): The GMCH is always enabled as a master on HI. This bit is

 

hardwired to a 1. Writes to this bit position have no effect.

 

 

1

Memory Access Enable (MAE): The GMCH always allows access to main system memory. This

 

bit is not implemented and is hardwired to 1. Writes to this bit position have no effect.

 

 

0

I/O Access Enable (IOAE): This bit is not implemented in the GMCH and is hardwired to a 0.

 

Writes to this bit position have no effect.

 

 

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D15343-003

Page 52
Image 52
Intel D15343-003 manual Pcicmd PCI Command Register, = Serr message is not generated by the Gmch for Device #0