2008-10-20 04:47:23 why CF/True IDE interface with BF531 write speed is slow
crystal shark (CHINA)
In my BF531 board , i used the schematic from :
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 ?
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.
2008-10-20 05:02:05 Re: why CF/True IDE interface with BF531 write speed is slow
Sonic Zhang (CHINA)
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.