1. Reconfigurable Architectures

2. 2 Granularity of Reconfigurable Systems Granularity:  The abstraction level used to configure the device.  May use a −Boolean-level, −instruction-level, −function-level, −process-level representation.

3. 3 Granularity of Reconfigurable Systems Granularity:  Proportional to the length of a configuration: −Fine/low-grain: long configuration −Course grain (high-level granularity): short configuration Fine-grain (Boolean-level) architecture:  FPGA: −Primary computational elements: limited-input LUTs  Suitable for simple to complex Boolean functions. −Inefficient for complex functions like multipliers Instruction-level:  Has computational units that perform instruction-level operations  Units vary from byte-width to word-width (32-bit) datapath operations.  Units rarely have states: −Read from registers and written to registers  Efficient for performing instructions but inefficient at performing Boolean operations.

4. 4 Granularity Freedom of device:  Instruction-level granularity only allows a limited number of register locations and small number of operations (on those locations)  Lower granularity level allows more locations and different complex customized FUs. −Can implement complex functions by a number of LUTs. Efficiency:  The more closely the application operation is matched to the granularity, the more efficient the device will execute. Example:  DSP application needs a lot of word-size add and mult. −  instruction-level granularity.  Application with a lot of Boolean operations: −  Boolean-level granularity.

5. 5 Granularity Functional-level:  Units are complex multi-cycle operations −Extensible processors with customized instructions. Process-level:  Extremely complex processes which often take 100- 1000 cycles to complete.  Example: −A cryptography device which decides on the algorithm based on the input key.

6. 6 Hybrid Devices Recent commercial FPGA devices with multiple levels of granularity:  LUTs,  Dedicated adders/multipliers,  DSP units.

7. 7 Granularity  Course-grained reconfigurable devices (rDPA)  Fine-grained reconfigurable devices (FPGA) [Hartenstein07]

8. 8 Area Efficiency

9. 9 References [Hartenstein07] Hartenstein, “Basics of Reconfigurable Computing,” S. P. J. Henkel, Ed. New York: Springer- Verlag, 2007. [Kastner04] Kastner, Kaplan, Sarrafzadeh, “Synthesis techniques and optimizations for reconfigurable systems,” Kluwer, 2004.