VLIW Instruction Pointer Extraction for Memory Width Reduction

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Solution Overview

Problem

The high bandwidth requirements and physical space needs of Very Long Instruction Word (VLIW) processors due to the wide instruction words lead to increased costs and complexity, as they necessitate wide instruction memories and data paths.

Innovation Solution

Implementing instruction pointers within VLIW processors, where a fetch unit identifies and retrieves instructions from pre-loaded instruction windows, reducing the need for explicit instruction inclusion in the very long instruction words and minimizing the width of instruction memory and data paths.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If very long instruction words include multiple instructions to enable concurrent execution, then processor performance is improved, but bandwidth requirements and physical space increase

Engineering Contradiction:

Improveprocessor performanceVSAvoidbit length of instruction words

Core Design Contradiction:

ProductivityVSQuantity of substance

Solution Approach 1:

The patent extracts only the essential addressing information (instruction pointers) from the full instruction words. Instead of transmitting complete multiple instructions within each VLIW, the system transmits compact pointers that reference instructions pre-loaded in instruction windows, significantly reducing the bit length while maintaining the ability to execute multiple instructions concurrently

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent employs preliminary action by pre-loading instructions into instruction windows before they are needed for execution. This allows the instruction pointers in the VLIW to reference already-available instructions in the instruction windows, eliminating the need to transmit full instruction data and reducing bandwidth requirements

Inventive Principle:

Principle #10Preliminary action

2Productivity

If wide instruction memory and data paths are used to accommodate VLIW width, then concurrent instruction execution is enabled, but device complexity and cost increase

Engineering Contradiction:

Improveconcurrent instruction execution capabilityVSAvoidinstruction memory width and data path width

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent extracts only the necessary pointer information from full instructions, allowing the use of narrower instruction memory and data paths. The instruction windows serve as intermediate storage, enabling the system to work with compact pointers rather than wide instruction words, thus reducing device complexity while preserving concurrent execution capability

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The instruction windows act as an intermediary structure between the compact VLIW format and the functional units. This intermediary allows the system to use narrow data paths for pointer transmission while still supporting wide instruction execution capabilities, effectively decoupling the pointer width from the instruction execution width

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS8095775B1Instruction pointers in very long instruction words

Publication Date: 2012.01.10 MARVELL ASIA PTE LTD

AI summary

During operation of a VLIW processor, a very long instruction word is fetched. A portion of the very long instruction word that includes a pointer to an instruction is identified, and the instruction pointed to by the pointer is retrieved from a location of an instruction window. The retrieved instruction is input into a functional unit for execution.