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S. Ziavras HW Design Considerations for Speculation
Register renaming vs. reorder buffers
Instead of ROB, explicitly use larger physical set of
regs. combined with reg. renaming
All results are allocated a new virtual reg. until
results are allocated new virtual reg.
PowerPC 603/604 series, MIPS R10000/12000, Alpha
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 &
begin processing event, when in fact speculation was
– Most pipelines with specu...
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- Fall '09