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Politics : Formerly About Advanced Micro Devices
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To: Hans de Vries who wrote (98814)3/17/2000 6:32:00 PM
From: Daniel Schuh  Read Replies (1) of 1571685
 
Hans, this brings up a puzzle I noticed in the Willamette software developer's guide, the link was posted here around IDF time with all the hype. From Section 4.2.


4.2. NOTABLE DIFFERENCES BETWEEN THE WILLAMETTEAND P6 FAMILY PROCESSORS
The following sections highlight some notable differences between Willamette and the P6family processors that affect code performance.

4.2.1. Code Selection
? The decoder template restrictions found in the P6 family processor no longer apply with
the Willamette family processors.
? Shifts are relatively much more expensive in Willamette family processors, and multiplies are somewhat more expensive.

My own reading of that little tidbit is that slick Willy doesn't have a barrel shifter, and that you're perhaps being quite optimistic about the cost of shift instructions there. I'd guess it's really a cycle per bit shifted, i.e. a<<3 is three cycles at least. Just a guess, though.

Cheers, Dan.
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