Hi Dennis Bieber Thank you for the detailed explanation of the SD card standard (class) and features.
>The SanDisk Class 4 was easily 8 times faster than the Kingston Class >10 for regular write, rewrite, and random write, and was also faster (if >not as much) for read/reread/random read. We will use it as a reference when selecting an SD card. It turns out that like SD cards, MMCs have completely different transfer rates. >https://en.wikipedia.org/wiki/MultiMediaCard#Table so many version... Is the transfer speed of MMC completely different like SD card? regards, 2021年2月24日水曜日 9:07:48 UTC+9 RobertCNelson: > On Tue, Feb 23, 2021 at 5:59 PM ha ppay <[email protected]> wrote: > > > > Hi RobertCNelson, > > > > I recently knew that the SD card was just one type of MMC, but I just > made a mistake. Thank you for your advice. > > yes, I knew that the am335x MMCHS supports up to 4-bit mode on SD cards. > > PS you can cat the debugfs to find out what mode this is in: > > MicroSD: 4-bit mode > debian@bbb-pwr01-ser09:~$ sudo cat /sys/kernel/debug/mmc0/ios > clock: 50000000 Hz > vdd: 21 (3.3 ~ 3.4 V) > bus mode: 2 (push-pull) > chip select: 0 (don't care) > power mode: 2 (on) > bus width: 2 (4 bits) > timing spec: 2 (sd high-speed) > signal voltage: 0 (3.30 V) > driver type: 0 (driver type B) > > eMMC: 8-bit mode > debian@bbb-pwr01-ser09:~$ sudo cat /sys/kernel/debug/mmc1/ios > clock: 52000000 Hz > vdd: 21 (3.3 ~ 3.4 V) > bus mode: 2 (push-pull) > chip select: 0 (don't care) > power mode: 2 (on) > bus width: 3 (8 bits) > timing spec: 1 (mmc high-speed) > signal voltage: 0 (3.30 V) > driver type: 0 (driver type B) > > If you can't read that, then update your fstab: > > debian@bbb-pwr01-ser09:~$ cat /etc/fstab | grep debug > debugfs /sys/kernel/debug debugfs mode=755,uid=root,gid=gpio,defaults 0 0 > > Regards, > > -- > Robert Nelson > https://rcn-ee.com/ > -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/3d51bd1b-0c02-497f-a61c-e7b9caf1b937n%40googlegroups.com.
