chapter3-m6-ziavras

Ziavras hw design considerations for speculation

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Unformatted text preview: h respect to all earlier Ls S. Ziavras HW Design Considerations for Speculation Register renaming vs. reorder buffers • Instead of ROB, explicitly use larger physical set of ROB regs. combined with reg. renaming • All results are allocated a new virtual reg. until results are allocated new virtual reg. they commit • PowerPC 603/604 series, MIPS R10000/12000, Alpha 21264 21264, Pentium II/III/4 – Reg. renaming adding 20-80 extra regs. S. Ziavras HW Design Considerations for Speculation (2) How much to speculate • Significant disadvantage of speculation: processor may speculate that some costly exceptional event occurs & th begin processing event, when in fact speculation was incorrect – Most pipelines with specu...
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