8050D N/B Maintenance
5.2 Intel 855GM/GME North Bridge(4)
AGP Status Signal Descriptions
Signal Name | Type |
|
GST[2:0] | O | Status: Provides |
| AGP | information from |
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| the arbiter to an |
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| AGP Master on |
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| what it may do. |
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| ST[2:0] only |
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| have meaning |
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| to the master |
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| when its GNT# is |
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| asserted. When |
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| GNT# is |
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| deasserted |
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| these signals have |
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| no meaning and |
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| must be gnored. |
AGP Flow Control Signals
|
| Description |
|
| Signal Name | Type | Description |
ST[2:0 | Meaning |
|
| GRBF# | I | Read Buffer Full: Read buffer full indicates if the master is ready to | |
000 |
| Previously requested low priority |
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| AGP | accept previously requested low priority read data. When RBF# is | |
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|
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| asserted the GMCH is not allowed to initiate the return low priority | |||
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| read data is being returned to the |
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| read data. That is, the GMCH can finish | |
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| master arbiter to an AGP |
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| returning the data for the request currently being serviced. RBF# is | |
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| only sampled at the beginning of a cycle. |
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| If the AGP master is always ready to accept return read data then it is |
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|
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| not required to implement this signal. |
001 |
| Previously requested high priority |
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|
| During FRAME# Operation: This signal is not used during AGP | |
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|
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| FRAME# operation. | |||
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| read data is being returned to the |
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| ||
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| GWBF# | I | |||
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| master |
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| |||
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| Secret | AGP | Write data from the GMCH. When WBF# is asserted the GMCH is | ||
010 |
| The master is to provide low priority | |||||
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| not allowed to drive Fast Write data to the AGP master. WBF# is | |||||
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| write data for a previously queued |
| ||||
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| only sampled at the beginning of a cycle. | ||||
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| write command |
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| |||
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| If the AGP master is always ready to accept fast write data then it is | |||
011 |
| The master is to provide high |
| ||||
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| not required to implement this signal. | |||||
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| priority write data for previously |
| ||||
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| During FRAME# Operation: This signal is not used during AGP | ||||
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| queued write command. |
| ||||
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| |||
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|
| FRAME# operation. | ||
100 |
| Reserved |
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| |
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|
| Document | ||||
101 |
| Reserved MiTac | |||||
110 |
| Reserved |
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|
111 |
| The master has been given |
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|
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| |
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| permission to start | bus transaction. |
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| Confidential |
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| ||||
The master may queue AGP requests by asserting PIPE# or start a PCI transaction by asserting FRAME#
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