2008-10-20 04:47:23     why CF/True IDE interface with BF531 write speed is slow

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2008-10-20 04:47:23     why CF/True IDE interface with BF531 write speed is slow

crystal shark (CHINA)

Message: 63932   

 

 

 

In my BF531 board , i used the schematic from :

 

     http://docs.blackfin.uclinux.org/doku.php?id=linux-kernel:drivers:ide-blackfin

 

After a few days' effort , it can work now ,but i think the write speed is slow. Can you give me some suggestion to get a higher write speed ?

 

root:~> mount

rootfs on / type rootfs (rw)

proc on /proc type proc (rw)

ramfs on /var type ramfs (rw)

sysfs on /sys type sysfs (rw)

devpts on /dev/pts type devpts (rw)

debugfs on /sys/kernel/debug type debugfs (rw)

securityfs on /sys/kernel/security type securityfs (rw)

/dev/hda1 on /mnt type ext2 (rw,sync)

 

We mount it with "-o sync",because we want to write lots of data that much more larger than the sdram size into the cf card and alse have the time limitiation.

 

The simple read test:

 

root:~> ls /mnt -l

-rwxr-xr-x    1 root     root           51 Apr  8 01:37 dd_test.sh

drwx------    2 root     root        12288 Jul  7  1921 lost+found

-rw-r--r--    1 root     root           33 Dec  1  1922 mmc.sh

-rw-r--r--    1 root     root         4604 Jul 13 01:44 reg.ko

-rw-r--r--    1 root     root      5242880 Jul 13 01:49 test

 

root:~> time cat /mnt/test > /dev/null

real    0m 0.17s

user    0m 0.00s

sys     0m 0.17s

 

 

The read speed is very good , about 5M/0.17s = 29 M/s . I do not know whether it is right to calculate the read speed.

 

But the write speed is too slow:

 

root:~> time dd if=/dev/zero of=/mnt/test bs=5M count=1

1+0 records in

1+0 records out

real    0m 4.65s

user    0m 0.00s

sys     0m 0.67s

 

 

It is around 5/4.65 = 1.1 MB/s

 

But we need read/write speed above 5MB/s  for our application . And the copy speed is slower than the  dd

 

Our CF card is 133X , I think it is fast enough.

 

 

 

 

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2008-10-20 05:02:05     Re: why CF/True IDE interface with BF531 write speed is slow

Sonic Zhang (CHINA)

Message: 63936   

 

CF write speed depends on the flash chip it uses. Not all manufaturers are honest on its label.

 

In addition, 133x and above high speed CF needs UDMA capable IDE controller and driver, which true ide interface with BF531 is definitely not.

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