Processor Director for Extended Memory Access
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Solution Overview
Problem
Computing architectures face limitations in accessing large amounts of RAM due to limited address modes, which restrict processors to 16-bit or 32-bit addresses, leading to performance slowdowns when trying to access memory locations beyond these limits, especially when interacting with memory-mapped I/O devices.
Innovation Solution
A processor director system that couples processors to system memory, using a configuration register to store and retrieve target addresses, allowing processors to access memory locations beyond their native address limits by mapping special addresses to extended addresses, thereby enabling access to higher memory ranges without requiring complex unique logic.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If software solutions are used to ensure memory access conforms to address limitations, then memory access is enabled within address limits, but performance is slowed
Solution Approach 1:
A processor director is introduced as an intermediary component between the processor and system memory. The processor director includes configuration registers that store target addresses and logic that intercepts memory access requests, checks them against the stored addresses, and either permits or blocks access accordingly. This hardware-based intermediary eliminates the need for software intervention, thereby maintaining full processing performance while enforcing address limitations.
2Device complexity
If processors are limited to 16-bit or 32-bit addresses in certain modes, then address space access is simplified, but access to larger memory locations is restricted
Solution Approach 1:
The processor director extends the effective address space by adding an additional dimension through configuration registers. These registers store target addresses that map limited address mode requests to extended memory locations. When a processor issues a memory access request in limited address mode, the processor director retrieves the corresponding target address from the configuration register, effectively translating the limited address into a full address space access without requiring the processor itself to support larger address modes.
3Reliability
If system software is used to manage memory access, then address limitations are enforced, but implementation complexity increases
Solution Approach 1:
The patent replaces the software-based memory access management mechanism with a hardware-based processor director. The processor director contains dedicated configuration registers for storing target addresses and built-in logic for intercepting and evaluating memory access requests. This hardware implementation provides more reliable and deterministic enforcement of address limitations compared to software solutions, while reducing overall system complexity by eliminating the need for complex software management routines.
Data Source
AI summary
Supporting limited address mode memory access involves receiving a write request from the processor targeted to a first predetermined address. A data portion of the write request includes a target address of the system memory. In response to determining the write request is targeted to the first predetermined address, the target address is sent via a system interface to be stored in a configuration register of the processor director. A memory access request targeted to a second predetermined address is received from the processor. In response to determining the memory access request is targeted to the second predetermined address, the target address is retrieved from the configuration register of the processor director. The memory access is serviced using the target address retrieved from the configuration register.