Thread: SDHC SD possible with N770
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fanoush is offline fanoush
2007-12-08 , 11:39
Posts: 2,152 | Thanked: 1,490 times | Joined on Jan 2006 @ Czech Republic
#7
Originally Posted by serge48 View Post
Here it is (SanDisk microSD 4G SDHC):

Code:
[    7.490966] mmc0: Problem switching card into high-speed mode!
..
..
[    7.498931] mmci-omap mmci-omap.2: command timeout (CMD8)
[    7.499084] mmci-omap mmci-omap.2: command timeout (CMD8)
[    7.505523] mmci-omap mmci-omap.2: card status error (CMD13)
This happens with some Sandisk cards even in N800 or other devices. Not sure if it is Sandisk's fault or what. Looks like the card tells first that is supports high speed mode and then returns error when it is tried. Maybe it simply does not support high-speed mode. If you get read speed over 12MB/s (25MHz with 4 bit bus) with usb reader and this card than it does support high speed mode and something else is wrong.

Originally Posted by serge48 View Post
Write :
Code:
Nokia-770-36:~# sync; time sh -c "dd if=/dev/zero of=/media/mmc1/testfile bs=1M count=100;sync"
100+0 records in
100+0 records out
real    0m 40.60s
user    0m 0.00s
sys     0m 4.92s
Read :
Code:
Nokia-770-36:~# time dd if=/media/mmc1/testfile of=/dev/null bs=1M
100+0 records in
100+0 records out
real    0m 38.41s
user    0m 0.00s
sys     0m 2.63s
Yes MMC bus speed is limit, 24MHz over 1 bit = max. 3MB/s in theory.

Thanks for testing. It is great it works. Could you read whole card (dd with if=/dev/mmcblk0 and no 'count') to verify that blocks over 2GB are read correctly? It will take long time. Or you could even try writing too, just filling your whole first partition with dd would be a good test too.

Or if you boot from ext2 partition located at the end of the card it should be OK too.

I hope I will test it soon too. I have Transcend 4gb mini SDHC class 4 card waiting for this. It does support high speed mode in N800.
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