[HC2] eMMC module removed ?

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[HC2] eMMC module removed ?

Unread postby ubujoe » Sat Aug 04, 2018 9:43 pm

Hello everybody,

I am particularly interest in buying a HC2 but I could notice that this board doesn't support eMMC card for boot media.
XU4 board have the support eMMC and the HC2 board come from the XU4 board with sata plug.

So I am surprised not to find in the technical details the eMMC support : https://www.hardkernel.com/main/product ... 1505170472

Can you confirm me that the eMMC support has been removed on the HC2 ? The only media for booting is the sd-card.
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Re: [HC2] eMMC module removed ?

Unread postby mad_ady » Sat Aug 04, 2018 10:08 pm

Yes, emmc has been removed probably to reduce cost. You can boot only from sd, but minimally the sd must hold only uboot and kernel, while the root filesystem can live on hdd
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Re: [HC2] eMMC module removed ?

Unread postby ubujoe » Sun Aug 12, 2018 6:20 pm

Okay that's too bad

I just read in the user manual of XU4 that the transfer rate of sd is approximately 30MB/s : https://magazine.odroid.com/odroid-xu4

I learned that there is 2 data transfer modes on the sd-card such as SDR50 and SDR104. We can see speed of 90MB/s on the label of sd-card sold in the shop but unfortunately the SDR50 mode is used on the SBC which limits the data rates to 50Mb/s.

Why do you tell me that the sd must hold only uboot and kernel and not the root filesystem ? (because of restricted data rates of 30MB/s on the sd-card )?
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Re: [HC2] eMMC module removed ?

Unread postby meveric » Sun Aug 12, 2018 7:03 pm

ubujoe wrote:Why do you tell me that the sd must hold only uboot and kernel and not the root filesystem ? (because of restricted data rates of 30MB/s on the sd-card )?

It means you can export the rootfs to a faster SSD/HDD instead and have much faster access speed than from SD card, if that's a preferred scenario. It's a "can do" not a "have to".
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Re: [HC2] eMMC module removed ?

Unread postby mad_ady » Sun Aug 12, 2018 7:30 pm

You can do two things:
* use the sd for uboot and kernel and move the rootfs to HDD (preferably ssd). The only problem is if it's a mechanical drive it might not get to go to sleep because of os activity/logs
* use the sd for uboot, kernel and rootfs and the hdd is just for data. A good sd card is recommended.
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