Module Power Down does not work

We use SM470R1B1M in one project. In order to reduce the power consumption, we want to power down some unused modules, for example, SPI module. The following is the related code:

CLKCNTL |= 0x80;        //Stop the clock to one module if that module is not used;

SPI1CTRL2 |= 0x04;   //Power Down SPI 1 module;

SP21CTRL2 |= 0x04;   //Power Down SPI 2 module;

 I use multimeter to meausre the current of 1.8V core supply.

First, I commented out above code to disable power down, I meausred the current, the current is 68.5mA;

Then I enabled the power down and measured the current again, the current is almost the same, 68.4mA.

So it appears that the power down unused module does not help much for power consumption reduction. 

I also tried to chang the frequency of sysclock and found that the current consumption drops as expected.