I tested SH which seems to run same speed as ASH.
Below SH Script blinks GPIO16 LED at about 1Hz:


#!/bin/sh
## blkTmrSh

X=0
C16=0
#while [ $X -le 100000 ]
while [ $X -le 77000 ]
do
#  echo $X
  X=$((X+1))

  C16=$((C16+1))
  if [ $C16 -eq 1500 ]; then
    echo "1" > /sys/class/gpio/gpio16/value
  fi
  if [ $C16 -gt 3000 ]; then
    echo "0" > /sys/class/gpio/gpio16/value
    C16=0
  fi
done