
4/29/2020
Godson 3A2000 / 3B2000 Processor User Manual
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2 needs to be set to 0
1 Use external PCI arbitration
0 Use SPI boot function
2.3 Cache
consistency
Loongson 3A2000 maintains the cache consistency between the processor and the I / O accessed through the HT port by hardware, but
The hardware does not maintain the cache consistency of I / O devices connected to the system through PCI. During driver development,
When PCI access devices perform DMA (Direct Memory Access) transmission, the software needs to perform Cache consistency
maintain.
2.4 Distribution of physical address space at the node level of the system
The system physical address distribution of Loongson No. 3 series processors adopts a globally accessible hierarchical addressing design to
System development is compatible with expansion. The physical address width of the entire system is 48 bits. According to the upper 4 bits of the address, the entire address is empt
Time is evenly distributed to 16 nodes, that is, each node is allocated 44-bit address space.
Loongson 3A2000 processor can directly use 4-chip direct connection to build CC-NUMA system, the processor number of each chip
Determined by the pin NODEID, the address space of each chip is distributed as follows:
Table 2-2 Node-level system global address distribution
Chip node number (NODEID)
Address [47:44] bits
starting address
End address
0
0
0x0000_0000_0000
0x0FFF_FFFF_FFFF
1
1
0x1000_0000_0000
0x1FFF_FFFF_FFFF
2
2
0x2000_0000_0000
0x2FFF_FFFF_FFFF
3
3
0x3000_0000_0000
0x3FFF_FFFF_FFFF
Loongson 3A2000 uses a single node 4-core configuration, so Loongson 3A2000 chip integrated DDR memory controller, HT
The corresponding addresses of the bus and PCI bus are contained in the 44-bit field from 0x0 (inclusive) to 0x1000_0000_0000 (not included)
Within each node, the 44-bit address space is further evenly distributed to a maximum of 8 devices that may be connected within the node.
Among them, the lower 43 bits of addresses are owned by 4 shared cache modules, and the higher 43 bits of addresses are further according to the address [43:42] bits
Distribute to devices connected to 4 directional ports. According to the different configuration of the chip and system structure, if there is no
If there is a connected slave device, the corresponding address space is reserved address space, and access is not allowed.
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The slave devices corresponding to the address space of the first-level crossbar in the Loongson 3A2000 chip are as follows:
Table 2-3 Address distribution in nodes
device
Address [43:41]
Start address within the node
Node end address
Shared Cache
0,1,2,3
0x000_0000_0000
0x7FF_FFFF_FFFF
HT0 controller
6
0xC00_0000_0000
0xDFF_FFFF_FFFF