Processor Branch on Overflow for 64-bit Addressing
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Solution Overview
Problem
Current microprocessor architectures, particularly RISC architectures, face limitations in addressing large memory spaces and supporting 64-bit operations due to fixed instruction lengths and limited immediate value representation, which restricts the range of branch or jump instructions and hinders efficient execution of operations across the entire 64-bit address space.
Innovation Solution
The processor design includes an Arithmetic and Logic Unit (ALU) capable of performing arithmetic operations and checking for overflow or underflow, with an instruction unit that branches based on these conditions, and uses specific instruction sequences like ATI, AHI, and AUI to manipulate 64-bit registers directly, allowing for more flexible and efficient addressing of large memory spaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If fixed instruction lengths are used in RISC architecture, then instruction decoding is simplified and pipeline execution is improved, but the range of addressable memory space is limited and 64-bit operations cannot be efficiently supported
Solution Approach 1:
The patent segments the 64-bit address space handling into multiple instruction formats. Some instructions use fixed-length formats for simple operations, while others use variable-length formats or extended formats that can address the full 64-bit space. This segmentation allows the processor to maintain simple fixed-length instruction processing for common operations while providing extended addressing capability when needed.
Solution Approach 2:
The patent introduces additional dimensions to the instruction set architecture by adding new instruction formats and opcodes that extend beyond the traditional fixed-length RISC instruction format. This includes adding variable-length instruction support and extended immediate value fields, effectively adding a new dimension of flexibility to the originally rigid fixed-length instruction structure.
2Device complexity
If limited immediate value representation is used, then instruction format remains compact and simple, but the range of branch or jump instructions is restricted
Solution Approach 1:
The patent makes the instruction format dynamic by allowing the immediate value field size to vary based on the specific instruction type and addressing mode required. Instead of a static fixed-length immediate field, the processor can dynamically adjust the number of bits used for immediate values, allowing compact encoding for small ranges and extended encoding for larger address spaces when needed.
Solution Approach 2:
The patent changes the parameters of the instruction format by introducing variable immediate value widths and multiple addressing modes. The immediate value representation is no longer fixed but can be adjusted as a parameter based on the specific operation requirements, allowing the same instruction template to serve multiple purposes with different address ranges.
3Ease of operation
If traditional RISC instruction sequences are used to achieve large arbitrary values, then instruction execution is straightforward, but the number of instructions required increases and execution efficiency decreases
Solution Approach 1:
The patent implements preliminary action by pre-computing and caching address components in dedicated registers before they are needed for memory access. The processor performs preliminary address generation and breaks down 64-bit addresses into manageable components that can be prepared in advance, reducing the number of instructions needed during actual memory operations and improving execution efficiency.
Data Source
AI summary
A method provides for decoding, in a microprocessor, an instruction into data identifying a first register, a second register, an immediate value, and an opcode identifier. The opcode identifier is interpreted as indicating that an arithmetic operation is to be performed on the first register and the second register, and that the microprocessor is to perform a change of control operation in response to the addition of the first register and the second register causing overflow or underflow. The change of control operation is to a location in a program determined based on the immediate value. A processor can be provided with a decoder and other supporting circuitry to implement such method. Overflow/underflow can be checked on word boundaries of a double-word operation.