Exploiting Detachability

1. Exploiting Detachability Hashem H. Najaf-abadi Eric Rotenberg

2. Different jobs, Different tools • Different applications have different characteristics and therefore different resource needs. • Therefore a single fixed architecture compromises the performance of the individual, for the performance of all.

3. Architectural changeability(Transformation) • In silicon-based technology; performance of a changeable (polymorphic) design in a fixed configuration is less than a non-changeable implementation of the same configuration.

4. Changeability at any level of the design hierarchy Changeability in subcomponent Interacting subcomponents may need to change too Changeability in interconnect Sub-component Interconnect

5. In an adder for instance; Changeability at logic-circuit level carry F.A. F.A. F.A. F.A. • Or the bypasses; F.U. F.U. F.U. F.U.

6. In the execution for instance; Changeability at the pipeline level fetch decode dispatch issue execute execute write-back

7. At least there’s no higher level for changeability to spread to. Changeability at the processor level Core A Core B Core C L2 cache

8. Heterogeneity • Pros: • No low-level changeability • Cons: • Poor scalability (die area is consumed, burdening access to system resources) • Inflexible (once configurations are placed in the system, they are permanent, while their need is user dependent)

9. Spread Heterogeneity to numerous chips • Pros: • Increases the overall die area, thus ameliorating the unscalability • Cons: • Exacerbates the burdening of access to system resources • Remains inflexible in the forms of architectural diversity that are made available

10. Exploiting Detachability • Detachability: a property that already exists (due to marketing and packaging issues). • Pros: • No suboptimality due to limited die are or burdening of access to system resources. • Flexible in the forms of architectural diversity

11. Exploiting Detachability • Other advantages: • A substrate for gradual employment of alternate technologies (which tend to be application dependent) • A paradigm where architects can focus on innovations for enhancing architectures for specific applications, rather than tweaking the same old design.

12. Changeability in real world applications • Rough automatic design-space exploration for the integer SPEC2000 benchmarks • Randomly varied the L1 and L2 cache sizes, the processor width, issue queue size, and clock period.

13. Customization results

14. On each other’s Rows indicate benchmarks, and columns indicate the their customized architectures

15. 3 6 1 7 4 5 2 Representative architectures • Assigning surrogates: gcc parser vortex mcf gzip twolf crafty perl gap vpr bzip

16. Customization results