Why gfortran`s stream access is so slow?

[shark <cplusplus09 at gmail dot com>]

Hi, everyone, i want to why gfortran`s stream read write is so slow?
>From gfortran`s manual, i know that gfortran`s I/O are buffered on
default, so it should be ok while reading bytes and bytes.
For testing, i wrote programs below:
----------------------------------------------C
Version---------------------------------------------
#include <stdio.h>
#include <stdlib.h>
int main(int argc, char * argv[])
{
  if(argc!=3)
    {
      printf("no enought parameters!\n");
      return -1;
    }
  FILE *srcFile,*destFile;
  unsigned char byte;
  int i,len;
  srcFile=fopen(argv[1],"rb+");
  destFile=fopen(argv[2],"wb+");
  fseek(srcFile,0,SEEK_END);
  len=ftell(srcFile);
  printf("len=%d",len);
  rewind(srcFile);
  for(i=len;i>0;i--)
    {
      byte=fgetc(srcFile);
      fputc(byte,destFile);
    }
  fclose(destFile);
  fclose(srcFile);
  return 0;
}
------------------------------------------------GFortran--------------------------------------------

program fortCP
  character(len=256)        :: srcFile,destFile
  character                :: byte

  if(command_argument_count().ne.2)then
     print*,'agrument not enough!'
     stop
  end if
  call get_command_argument(1,srcFile)
  call get_command_argument(2,destFile)
 
open(10,file=trim(srcFile),form='unformatted',access='stream',status='old')
 
open(20,file=trim(destFile),form='unformatted',access='stream',status='replace')
  do
    read(10,end=500),byte
    write(20),byte
  end do 
500  close(20)
  close(10)
end program fortCP
--------------------------------------------------------------------------------------------------
Here`s the result.
32M File
GCC
real    0m2.925s
user    0m2.750s
sys     0m0.170s

GFORTRAN-4.2.2
real    9m48.880s
user    1m47.540s
sys     7m53.780s

export GFORTRAN_UNBUFFERED_ALL=n
real    10m0.607s
user    1m47.430s
sys     8m0.890s

export GFORTRAN_UNBUFFERED_ALL=y
real    10m1.754s
user    1m46.380s
sys     8m0.450s

Thanks every one.