Pass the Results, Please

April 1996 / Letters / Pass the Results, Please

In "AMD K6 Takes On Intel P6" (January), I came upon the term register-result bypassing in a context unfamiliar to me. Usually, this term is used to describe the bypassing of the register file so that the results of instructions just executed are forwarded to the following instructions in parallel with the write-back stage. But what you d escribe happens "without accessing main memory." Do you refer to stores forwarding data to loads in the store buffer as "register-result bypassing," or is it some other feature?
Gad S. Sheaffer
IDC & PPD Architecture
gss@iil.intel.com

I meant to indicate that the K6 can bypass registers to provide results to subsequent instructions and that stores can forward data to loads. In other word s, a load doesn't have to wait for a completed store instruction to put the result into memory; it can load the result directly from the store buffer.--Tom R. Halfhill, senior editor

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My approach to software engineering is far more pragmatic than it is theoretical--and no language better exemplifies this than C++.

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