64K

bilbo@localhost ~ $ dd if=/dev/random of=random bs=64K count=1
1+0 records in
1+0 records out
65536 bytes (66 kB, 64 KiB) copied, 0.000637442 s, 103 MB/s
for i in `seq 1 10`; do ./tools/ftdi_transfer write 0xac010000 random |& grep -E 'measured|crc'; done
remote crc: 2af6d258; local crc 2af6d258
   measured write time : 0.425  seconds
remote crc: 2af6d258; local crc 2af6d258
   measured write time : 0.425  seconds
remote crc: 2af6d258; local crc 2af6d258
   measured write time : 0.425  seconds
remote crc: 2af6d258; local crc 2af6d258
   measured write time : 0.425  seconds
remote crc: 2af6d258; local crc 2af6d258
   measured write time : 0.425  seconds
remote crc: 2af6d258; local crc 2af6d258
   measured write time : 0.425  seconds
remote crc: 2af6d258; local crc 2af6d258
   measured write time : 0.425  seconds
remote crc: 2af6d258; local crc 2af6d258
   measured write time : 0.426  seconds
remote crc: 2af6d258; local crc 2af6d258
   measured write time : 0.425  seconds
remote crc: 2af6d258; local crc 2af6d258
   measured write time : 0.425  seconds

1MB

dd if=/dev/random of=random bs=1M count=1
1+0 records in
1+0 records out
1048576 bytes (1.0 MB, 1.0 MiB) copied, 0.00464291 s, 226 MB/s
for i in `seq 1 10`; do ./tools/ftdi_transfer write 0xac010000 random |& grep -E 'measured|crc'; done
remote crc: de34b971; local crc de34b971
   measured write time : 6.666  seconds
remote crc: de34b971; local crc de34b971
   measured write time : 6.666  seconds
remote crc: de34b971; local crc de34b971
   measured write time : 6.663  seconds
remote crc: de34b971; local crc de34b971
   measured write time : 6.667  seconds
remote crc: de34b971; local crc de34b971
   measured write time : 6.667  seconds
remote crc: de34b971; local crc de34b971
   measured write time : 6.667  seconds
remote crc: de34b971; local crc de34b971
   measured write time : 6.665  seconds
remote crc: de34b971; local crc de34b971
   measured write time : 6.667  seconds
remote crc: de34b971; local crc de34b971
   measured write time : 6.664  seconds
remote crc: de34b971; local crc de34b971
   measured write time : 6.666  seconds

8MB:

dd if=/dev/random of=random bs=8M count=1
1+0 records in
1+0 records out
8388608 bytes (8.4 MB, 8.0 MiB) copied, 0.0240846 s, 348 MB/s
for i in `seq 1 10`; do ./tools/ftdi_transfer write 0xac010000 random |& grep -E 'measured|crc'; done
remote crc: 1c92e87c; local crc 1c92e87c
   measured write time : 53.247  seconds
remote crc: 1c92e87c; local crc 1c92e87c
   measured write time : 53.271  seconds
remote crc: 1c92e87c; local crc 1c92e87c
   measured write time : 53.245  seconds
remote crc: 1c92e87c; local crc 1c92e87c
   measured write time : 53.242  seconds
remote crc: 1c92e87c; local crc 1c92e87c
   measured write time : 53.242  seconds
remote crc: 1c92e87c; local crc 1c92e87c
   measured write time : 53.251  seconds
remote crc: 1c92e87c; local crc 1c92e87c
   measured write time : 53.271  seconds
remote crc: 1c92e87c; local crc 1c92e87c
   measured write time : 53.245  seconds
remote crc: 1c92e87c; local crc 1c92e87c
   measured write time : 53.242  seconds
remote crc: 1c92e87c; local crc 1c92e87c
   measured write time : 53.270  seconds

15MB:

dd if=/dev/random of=random bs=15M count=1
1+0 records in
1+0 records out
15728640 bytes (16 MB, 15 MiB) copied, 0.0500857 s, 314 MB/s
for i in `seq 1 10`; do ./tools/ftdi_transfer write 0xac010000 random |& grep -E 'measured|crc'; done

remote crc: 55797d82; local crc 55797d82
   measured write time : 99.868  seconds
remote crc: 55797d82; local crc 55797d82
   measured write time : 99.868  seconds
remote crc: 55797d82; local crc 55797d82
   measured write time : 99.870  seconds
remote crc: 55797d82; local crc 55797d82
   measured write time : 99.865  seconds
remote crc: 55797d82; local crc 55797d82
   measured write time : 99.822  seconds
remote crc: 55797d82; local crc 55797d82
   measured write time : 99.869  seconds
remote crc: 55797d82; local crc 55797d82
   measured write time : 99.819  seconds
remote crc: 55797d82; local crc 55797d82
   measured write time : 99.821  seconds
remote crc: 55797d82; local crc 55797d82
   measured write time : 99.871  seconds
remote crc: 55797d82; local crc 55797d82
   measured write time : 99.866  seconds