Method and apparatus for saving power in an integrated circuit

1. An integrated circuit (“IC”) comprising:

at least first and second circuits comprising a plurality of transistors operating at a first voltage; and

between the first and second circuits, a direct connection comprising a third circuit for transmitting a signal from the first circuit to the second circuit, wherein the third circuit is a buffer circuit comprising a transistor operating at a second voltage that is lower than the first voltage;

wherein at least one of the first and second circuits is a configurable circuit for configurably performing operations.

2. The IC of claim 1 , wherein the direct connection does not comprise any intervening configurable circuits.

3. The IC of claim 1 , wherein the direct connection further comprises a set of buffer circuits for receiving said signal before said third circuit receives said signal, said set of buffer circuits operating at the first voltage.

4. The IC of claim 1 , wherein both of the first and second circuits are configurable circuits for configurably performing operations.

5. The IC of claim 1 , wherein the configurable circuit is one of a configurable logic circuit for configurably performing logic operations and a configurable interconnect circuit for configurably performing interconnect operations.

6. The IC of claim 1 , wherein said buffer circuit is an inverter.

7. The IC of claim 6 , wherein said inverter comprises two NMOS transistors.

8. The IC of claim 1 , wherein at least one of the first and second circuits implements a logical signal as two complementary physical signals.

9. The IC of claim 1 , wherein the direct connection is at least partly implemented by differential signaling.

10. The IC of claim 1 , wherein said buffer circuit outputs a signal at the second voltage.

11. The IC of claim 1 , wherein said second circuit comprises a sub-circuit for level converting the signal from the second voltage to the first voltage.

12. The IC of claim 11 , wherein said sub-circuit comprises a set of cross-coupled transistors.

13. An integrated circuit (“IC”) comprising:

at least first and second circuits operating at a first voltage;

between the first and second circuits, a direct connection comprising a third circuit for transmitting a signal from the first circuit to the second circuit at a second voltage that is lower than the first voltage,

wherein the first circuit is a configurable circuit for configurably performing operations and said second circuit is a repeater for receiving said signal at a first current drive and for outputting said signal at a second current drive that is stronger than said first current drive.

14. An integrated circuit (“IC”) comprising:

first and second circuits operating at a first voltage; and

between said first and second circuits, a direct connection for carrying a logical value from the first circuit to the second circuit, said direct connection at least partly implementing differential signaling, said direct connection comprising:

first and second lines for carrying complementary first and second physical values that together represent the logical value,

wherein the first line comprises a first buffer for outputting the first physical value to the second circuit, the first buffer operating at a second voltage that is lower than the first voltage,

wherein the second line comprises a second buffer for outputting the second physical value to the second circuit, the second buffer operating at said second voltage.

15. The IC of claim 14 , wherein the first and second buffers are inverters.

16. The IC of claim 14 , wherein at least one of the first and second circuits is a configurable circuit.

17. The IC of claim 14 , wherein the first buffer outputs the first physical value at the second voltage.

18. The IC of claim 14 , wherein the second buffer outputs the second physical value at the second voltage.

19. The IC of claim 14 , wherein said first and second buffers each comprise two NMOS transistors.