lmbench analysis for RISCV

Hello,
I have built/run lmbench on RISCV HiFive Unleashed which has yocto linux kernel 5.4.3.
These are the results:
root@exaleapsemi:/mnt/kiran/lmbench3/bin/riscv64-linux-# ./bw_mem 1M rd
1.05 1770.58
root@exaleapsemi:/mnt/kiran/lmbench3/bin/riscv64-linux-# ./bw_mem 2M rd
***********************************************************
2.10 974.06
root@exaleapsemi:/mnt/kiran/lmbench3/bin/riscv64-linux-# ./bw_mem 3M rd
***********************************************************
3.15 600.90
root@exaleapsemi:/mnt/kiran/lmbench3/bin/riscv64-linux-# ./bw_mem 4M rd
***********************************************************
4.19 506.86
root@exaleapsemi:/mnt/kiran/lmbench3/bin/riscv64-linux-# ./bw_mem 200M rd
***********************************************************
209.72 424.38
root@exaleapsemi:/mnt/kiran/lmbench3/bin/riscv64-linux-# ./bw_mem 600M rd
***********************************************************
629.15 441.76
root@exaleapsemi:/mnt/kiran/lmbench3/bin/riscv64-linux-# ./bw_mem 879M rd
***********************************************************
921.70 437.99

Could some one please help me understand how we get 921.70 (last result) when 879Mb data is read and also the impact on speed, 437.99 Mbps?
Any other pointers will be helpful.

Thanks

Start by reviewing the reported bw_mem commands and outputs for the RISCV HiFive Unleashed running Yocto Linux kernel 5.4.3. Reproduce the 879M and larger reads if possible, then determine what 921.70 and 437.99 represent and document the explanation and speed impact.

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