rv32I-TangNano9K

RV32I Implementation on TangNano9K

You can run CoreMark Benchmark on this CPU. You can use UART.

five-staged-rv32i

simple CPU that execute 5 stage.

1	2	3	4	5	6	7	8	9	10
F	D	E	M	W
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five-pipeline-rv32i

CPU that execute 5 stage pipeline. This CPU has 2bit branching prediction and forwarding functions.

1	2	3	4	5	6	7	8	9	10
F	D	E	M	W
	F	D	E	M	W
		F	D	E	M	W
			F	D	E	M	W
				F	D	E	M	W
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Description by ChatGPT

Branching prediction is a technique used when processing branching instructions contained in the code of a program that the CPU executes. Branching instructions allow the program to branch to two different processing paths based on a condition contained within the program code. Examples of branching instructions include if statements and switch statements. The purpose of branching prediction is to shorten the time required to process branching instructions by predicting in advance which branching direction the branching instruction will take and processing the predicted direction first.

Forwarding is a technique that reduces the execution time of instructions by pre-fetching the necessary data before executing the instructions. The CPU can process multiple instructions at the same time, but this requires time to retrieve the data required by each instruction. By pre-fetching the data required by each instruction, the CPU can shorten the execution time of the instruction.

Resource used

name	PicoRV32	five-staged-rv32i	five-pipeline-rv32i
LUT	1951/8640	1360/8640	2748/8640
FF	799/6693	328/6693	783/6693
CLS	1207/4320	836/4320	1790/4320
BSRAM	3SDPB/1pROM	10SDPB/16pROM	7SDPB/16pROM
Max Clock	57.198Mhz	27.493Mhz	32.089Mhz
CoreMark/Mhz	About 0.4 (refer from this)	0.259	1.04

*PicoRV32 data is quoted from Interface 2022/12

memory map

Address	Size	Section
0x0000-0x0100	256B	unused
0x0100-0x6100	24KiB	.text(ROM)
0x6100-0x6900	2KiB	.rodata+.data+.bss+.comment(RAM)
0x6900-0x7d00	5KiB	stack(RAM)