Functional Description
R
Table 15. AGP Commands Supported by the Intel® MCH When Acting as an AGP Target
AGP | C/BE[3:0]# |
| MCH Host Bridge | |
Command | Encoding |
|
|
|
|
| Cycle Destination |
| Response as PCIx Target |
|
|
|
|
|
Read | 0000 | System memory |
| |
|
|
|
|
|
| 0000 | Hub interface |
| Complete with random data |
|
|
|
|
|
0001 | System memory |
| ||
|
|
|
|
|
| 0000 | The Hub interface |
| Complete with random data |
|
|
|
|
|
Reserved | 0010 | N/A |
| No response |
|
|
|
|
|
Reserved | 0011 | N/A |
| No response |
|
|
|
|
|
Write | 0100 | System memory |
| |
|
|
|
|
|
| 0100 | Hub interface |
| Cycle goes to DRAM with byte |
|
|
|
| enables inactive |
|
|
|
|
|
0101 | System memory |
| ||
|
|
|
|
|
| 0101 | Hub interface |
| Cycle goes to DRAM with byte |
|
|
|
| enables inactive; does not go to |
|
|
|
| the hub interface |
|
|
|
|
|
Reserved | 0110 | N/A |
| No response |
|
|
|
|
|
Reserved | 0111 | N/A |
| No response |
|
|
|
|
|
Long Read | 1000 | System memory |
| |
|
|
|
|
|
|
| Hub interface |
| Complete locally with random data; |
|
|
|
| does not go to the hub interface |
|
|
|
|
|
1001 | System memory |
| ||
Read |
|
|
|
|
|
|
|
|
|
|
| Hub interface |
| Complete with random data |
|
|
|
|
|
Flush | 1010 | MCH |
| Complete with QW of random data |
|
|
|
|
|
Reserved | 1011 | N/A |
| No response |
|
|
|
|
|
Fence | 1100 | MCH |
| No response; Flag inserted in |
|
|
|
| MCH request queue |
|
|
|
|
|
Reserved | 1101 | N/A |
| No response |
|
|
|
|
|
Reserved | 1110 | N/A |
| No response |
|
|
|
|
|
Reserved | 1111 | N/A |
| No response |
|
|
|
|
|
NOTES:
1. N/A refers to a function that is not applicable
As a target of an AGP cycle, the MCH supports all the transactions targeting system memory (summarized in Table 15). The MCH supports both normal and
Intel® 82845 MCH for SDR Datasheet | 113 |