MERSI protocol

A five-state cache-coherence protocol extending MESI with a Recent or Read-Only state to optimize shared cache-line ownership and response behavior in PowerPC G4 systems.

Version

v1 · 2026-09-08 · History

Domain-specific #

5543

Origin domain

computer architecture

Subdomain

computer architecture

Core Idea

MERSI tracks each cache line as Modified, Exclusive, Recent or Read-Only, Shared, or Invalid, using bus transactions and snooping rules to preserve a coherent memory view. State transitions assign dirty ownership, clean exclusivity, shared copies, and a designated recent responder so processors coordinate reads and writes while avoiding unnecessary memory responses. The abstraction is therefore identified by a declared carrier, a transformation or constraint over that carrier, and an invariant that tells an analyst whether the named structure is genuinely present.

Scope of Application

MERSI protocol belongs to computer architecture and is useful where the analyst can specify the typed computer architecture carrier, defining objects and relations, parameters, conventions, evidence, boundary cases, and comparison targets, then evaluate cache hierarchy, exact five state meanings, ownership and responder rule, bus events, snoop transitions, write policy, eviction, and memory-order assumptions match the named implementation. The scope is broad within that domain but bounded by the need for cache hierarchy, exact five state meanings, ownership and responder rule, bus events, snoop transitions, write policy, eviction, and memory-order assumptions match the named implementation. The entry records a descriptive analytical identity; practical use requires the governing domain's evidence, standards, and safety obligations.

Clarity

The abstraction clarifies a crowded vocabulary by making cache hierarchy, exact five state meanings, ownership and responder rule, bus events, snoop transitions, write policy, eviction, and memory-order assumptions match the named implementation the center of the account. A claim should name the carrier, the governing operation or relation, the applicable assumptions, and the recognition test. A bare label is insufficient because the name MERSI protocol can be used for a formal identity, an implementation, or a neighboring result unless carrier and convention are stated.

Manages Complexity

Without the abstraction, an analyst must reason directly over many local details: the carrier roles, admissibility assumptions, competing conventions, derived invariants, boundary cases, and proof or validation obligations specific to MERSI protocol. MERSI protocol compresses them into the roles in the structural signature. That compression permits comparison across instances without erasing the variables that determine validity. It also exposes which details may be varied safely and which are constitutive.

Abstract Reasoning

1. Identify the carrier. State what the elements, states, objects, or observations are: the typed computer architecture carrier, defining objects and relations, parameters, conventions, evidence, boundary cases, and comparison targets. Reject examples whose alleged carrier belongs to a different problem. 2. Lock the constitutive rule. Express cache hierarchy, exact five state meanings, ownership and responder rule, bus events, snoop transitions, write policy, eviction, and memory-order assumptions match the named implementation independently of one notation or implementation.

Knowledge Transfer

Knowledge transfers strongly among subfields of computer architecture because they reuse the typed computer architecture carrier, defining objects and relations, parameters, conventions, evidence, boundary cases, and comparison targets, State transitions assign dirty ownership, clean exclusivity, shared copies, and a designated recent responder so processors coordinate reads and writes while avoiding unnecessary memory responses., and type the carrier, state every parameter and convention in the definition, test that cache hierarchy, exact five state meanings, ownership and responder rule, bus events, snoop transitions, write policy, eviction, and memory-order assumptions match the named implementation, compare the nearest accepted identity, and report counterexamples, uncertainty, and limiting cases.

Relationships to Other Abstractions

Current abstraction MERSI protocol Domain-specific

Parents (1) — more general patterns this builds on

• MERSI protocol is a kind of Consistency Prime

  The proposed strict upward parent is prime:consistency.

Hierarchy path (1) — routes to 1 parentless root

• MERSI protocol → Consistency → Constraint

Neighborhood in Abstraction Space

MERSI protocol sits in a crowded region of the domain-specific corpus (24^th percentile for distinctiveness): several abstractions share nearly its structure, so a description that fits it tends to fit its neighbors too.

Family — Memory Architecture & Parallel Computing (34 abstractions)

Nearest neighbors

• Cache hierarchy — 0.93
• CPU cache — 0.92
• SHA instruction set — 0.91
• Firefly (cache coherence protocol) — 0.91
• Instruction-level parallelism — 0.91

Computed from structural-signature embeddings · 2026-09-08