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