eMMC to USB adapter "very" slow at reading data

[talpa]

Hi I have the Pine64 eMMC to USB adapter.

When reading (using dd to /dev/null) from the 64GB eMMC that came with the Pinebook Pro I only get around 15 MB/s
With the 128GB module I seem to recall around 13 MB/s

The 128 GB module does give me 157MB/s when inside the Pinebook Pro it self

I have tried playing with the block size of the dd reads but it doesn't seem to do much difference.

The USB adapter might only use 1 bit transfers cutting the bandwidth in quarter, but that should possibly still give me 39MB/s

Does anyone have any tips for getting more performance out of the adapter?

Regards Visti Andresen

[roncromberge]

Adapter is only usb2!


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[talpa]

Adapter is only usb2!


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Yes, but shouldn't USB 2 theoretically (aka. marketing lies) be capable of ~50MB/s

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According to the data sheet of the GL823 interface chip used it should support both 1 and 4 bit transfers.

However it also states a typical "SD/MMC Card Clock Frequency" of 48MHz i "High Speed Mode" which leaves one with 24MB/s of raw bandwidth to the eMMC if the interface runs in 4x mode.

I suppose protocol overhead could drop this down to 13-16 MB/s :o/

[talpa]

On a side note I'm getting around 50MB/s when dd'ing the data over ssh
(with a 1Gb/s ethernet connection with quite a lot of other traffic, and ssh did not use 100% of one CPU)

sudo dd if=/dev/mmcblk2 | ssh 192.168.9.30 dd of=/dev/null
965813760 bytes (2.0 GB, 1.8 GiB) copied, 37.0941 s, 53.0 MB/s

It seems that piping it through 'gzip -1' and 'zcat' only reduces the thoughput .

So perhaps I should just use the Pinebook Pro (booted of a SD card) as the eMMC reader