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Godson 3A2000 / 3B2000 Processor User Manual
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2. The original MC0 / 1_COMP_REF_RES is changed to NC pin. If the original 3A motherboard is used, no modification is required;
3. The original HT0 / 1_PLL_REF is changed to NC pin. If the original 3A motherboard is used, no modification is required;
4. The original MC0 / 1_COMP_REF_GND is changed to MC0 / 1_A15. If you use the original 3A motherboard, you don't need to repair it
Change; but if connected to a memory module, it can support a larger capacity
5. The function controlled by PCI_CONFIG [0] is changed to SPI startup enable. After setting to 1, it can be started from SPI FLASH. in case
Use the original 3A motherboard, you need to set it to 0 to start from LPC FLASH; if the motherboard already has SPI FLASH, you can
To connect GPIO [0] as SPI_CS and set PCI_CONFIG [0] to 1, start from SPI FLASH;
6. The function controlled by PCI_CONFIG [7] is changed to forced HT1.0 mode. After setting it to 1, HT starts directly in 1.0 mode.
If you use the 3A780E motherboard, you need to set it to 1 at present; if you use the 3A2H motherboard, no special settings are required;
7. CLKSEL [15:10] needs to be set to 6'b100001; if you need to use HT3.0 mode, you need to set CLKSEL [15:10]
Set to 6'b100101;
8. CLKSEL [9: 5] needs to be set to 5'b01111; use PMON to set the memory frequency;
9. CLKSEL [4: 0] needs to be set to 5'b01111; use PMON to set the processor core frequency;
10. For the 3A2H motherboard, you need to remove the pull-up resistors on HT0 / 1_powerok and HT0 / 1_resetn; (the original pull-up
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Godson 3A2000 / 3B2000 Processor User Manual Part 1
The resistance of 300 ohms is not suitable for 3A and can also be removed)
13.2 Frequency setting instructions
In order to be basically compatible with the frequency configuration of Godson 3A1000, the hardware frequency configuration range of Godson 3A2000 is narrow.
To obtain a wider frequency range and better clock quality, the software configuration in PMON is mainly used in Godson 3A2000
The configuration method is the same as Loongson 3B1500. Please refer to the PMON source code for the specific configuration method.
1. The frequency setting is completely set by the software, there is no need to modify CLKSEL when changing the frequency;
2. Stable working frequency of 1.15V core voltage: processor core frequency is set to 800MHz, memory frequency is set to 500MHz,
HT controller is set to 400MHz, HT bus 800MHz / 1600MHz;
13.3 PMON Change Guide
Compared with Loongson 3A1000, from the processor core, memory controller, HT controller to all levels of crossbar switches are different
Upgrade, so PMON needs to make some changes, mainly including the following necessary parts:
1. Remove the initialization operations of L1 Dcache, L1 Icache, Vcache, and L2 Cache after power-on (hardware completion);