
4/29/2020
Godson 3A2000 / 3B2000 Processor User Manual
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The numbers are 00, 01, 10, and 11, respectively. If you send a request from 11 to 00, it is a route from 11 to 00, first go in the X direction,
Go from 11 to 10, then go in Y direction, and go from 10 to 00. And when the response of the request returns from 00 to 11, the routing first goes
X direction, from 00 to 01, and then Y direction, from 01 to 11. As you can see, these are two different routing lines. by
Due to the characteristics of this algorithm, we will adopt different methods when constructing the interconnection of two chips.
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Godson 3A2000 / 3B2000 Processor User Manual Part 1
Two piece Loongson No. 3 interconnection structure
Due to the nature of the fixed routing algorithm, we have two different methods when constructing the interconnection of two chips. first of all
Using 8-bit HT bus interconnection. In this interconnection method, only 8-bit HT interconnection can be used between the two processors. Two chips
The numbers are 00 and 01 respectively. From the routing algorithm, we can know that when two chips access each other, they are connected to
8-bit HT bus at the same time. As follows:
Figure 10-3 Two-chip Loongson No. 3 8-bit interconnection structure
However, our widest HT bus can use 16-bit mode, so the connection method to maximize bandwidth should be
16-bit interconnect structure. In Godson III, as long as the HT0 controller is set to 16-bit mode, all are sent to the HT0 controller
Will be sent to HT0_LO instead of HT0_HI or HT0_LO according to routing table,
We can use the 16-bit bus when interconnecting. Therefore, we only need to correctly configure the 16-bit mode of CPU0 and CPU1
You can use the 16-bit HT bus interconnection to set and connect the high and low bus correctly. And this interconnect structure can also be used 8
Bit HT bus protocol for mutual access. The resulting interconnection structure is as follows:
Figure 10-4 Two-chip Loongson No. 3 16-bit interconnection structure
CPU0 HT0
HT
1
CPU1
HT0
16-bit HT bus
IO
16-bit HT bus
CPU0
HT0_
HI
HT0_
LO
HT
1
CPU1
HT0_
HI
HT0_
LO
8-bit HT bus
IO
16-bit HT bus
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