Browse Prior Art Database

Single-Operand Scheduling

IP.com Disclosure Number: IPCOM000018902D
Publication Date: 2003-Aug-20
Document File: 1 page(s) / 66K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method that uses a single-operand scheduler to track only one source in the scheduler. Benefits include a smaller scheduler that consumes less power.

This text was extracted from a Microsoft Word document.
This is the abbreviated version, containing approximately 87% of the total text.

Single-Operand Scheduling

Disclosed is a method that uses a single-operand scheduler to track only one source in the scheduler. Benefits include a smaller scheduler that consumes less power.

Background

Typically, instructions and operations (UOPs) have two inputs. Current schedulers track both inputs for a UOP, which allows the UOP to schedule when both of the sources are ready. Tracking both sources enables perfect scheduling, but comes at the cost of a larger scheduler.

General Description

The disclosed method realizes that one of the sources for a UOP is typically ready a long time before the UOP shows up in the scheduler. Another observation is that one of the sources is almost always ready after the other one, and that this repeats each time the UOP is executed.

At the time when the UOP is written into the scheduler, the disclosed method decides which source the scheduler should track. The decision is based on several inputs, including:

 

  • One source is ready at the time of writing the UOP into the scheduler, so it tracks the source that is not ready.
  • The source that was ready during the previous execution is remembered in a predictor.
  • UOP class and use heuristics are used in the decision; for example, for a load with a certain addressing mode, the available source is the one that changes most (base + index addressing).
  • Heuristic that source generated by the most recent previous uop, as determined by trace order, will be last source to become ready. This can be tracked dur...