FATSystem "BUG"?

Hi,
I have written some block device drivers, such as CF card, SD card, IDE
disk...There is a common problem.
For example, in CF card driver, I used the stream interface(XXX_init,
XXX_IoControl...). And I called the AdvertiseInterface() function to declare
it's a block device. So with the FAT system, we could see the mounted disk
in "My device" under WinCE. Then I copied files in & out of the disk to test
the W/R speed. I found that the write-in speed is 900KB/s, but the read-out
speed is no more than 500KB/s. That's insufferable.
I wrote an application to test R/W speed of CF card keep away from FAT: I
called CreateFile() to get the handle of the driver, then used
DeviceIocontrol() to write data in and read out. In this case, the Write
speed is 1.1MB/s, and the Read speed is more than 2MB/s.
And the same situation was appeared in SD card. With FAT: Write 1.2MB/s,
Read 500KB/s. Without FAT: Write 1.4MB/s, Read 4.1MB/s.
Even in the Ram Disk driver, the one used memory space as the virtual
storage space, the test result was: With FAT: Write more than 1.5MB/s, Read
600KB/s. With out FAT: all very fast speed.
So I thought the FAT system may cause the low efficiency of read operation
under WinCE.
Any suggestion is helpful and thankful.


.

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