GPu clock frequency

[rootkit]

[~]$ nvclock -n 10
Requested core clock:           10.000 MHz

Adjusted low-level clocks on a nVidia Geforce 7800GTX
Memory clock:   1296.000 MHz
GPU clock:      10.384 MHz

[~]$ nvclock -s
Card:           nVidia Geforce 7800GTX
Card number:    1
Memory clock:   1296.000 MHz
GPU clock:      10.384 MHz

[~]$

I don't really think that the GPU core is running at 10MHz, there are lower limit for GPU and RAM frequencies?