read-only memory
Enable an AI agent to recognise read-only memory, assess whether its stored contents can be read reliably, and determine which programming, replacement or protection actions its implementation permits.
Research draft, second pass
A second pass drafted this model: the structure a model of this thing needs, and what is known about it in the world. The line under this one says how the second half was obtained - researched against sources, or recalled without web access, in which case nothing here was read anywhere and every claim is a lead to verify. Unreviewed either way.
recalled by Codex without web access - no source was read
Researched by: Codex
Purpose and description
Enable an AI agent to recognise read-only memory, assess whether its stored contents can be read reliably, and determine which programming, replacement or protection actions its implementation permits.
Read-only memory (ROM) is nonvolatile digital memory whose contents are fixed during manufacture or programmed through a designated process and are read, rather than routinely rewritten, during normal operation.
It can be Classify a device or embedded region by its documented ROM implementation and physical boundary.; Determine compatible read conditions, addressing and interface settings.; Read accessible contents and compare them with an authorised, trusted reference.; Determine whether programming, erasure or protection changes are supported and whether each operation is reversible.; Assess retention and read-integrity evidence and identify when replacement or further diagnosis is needed.; Evaluate a proposed replacement against package, interface, timing, content and host compatibility..
Distinguishing features
The physical memory is intended to retain stored bits without continuous operating power; reading still requires the implementation's specified operating conditions.
Ordinary read operation does not provide unrestricted rewriting: content changes are impossible, one-time or dependent on a distinct programming or erasure mechanism.
A physical ROM device or region must be identifiable; a file called a ROM image is stored information rather than the memory hardware.
A RAM region with write permissions disabled does not become ROM merely because current software cannot write to it.
A flash or EEPROM implementation requires an explicit ROM classification or role; nonvolatility alone does not distinguish ROM from other storage.
Scope
+ Mask-programmed ROM, one-time-programmable ROM and explicitly identified erasable or electrically reprogrammable ROM implementations
+ Discrete ROM components and identifiable ROM regions embedded in larger devices
+ Storage organisation, addressing, read interfaces and electrical operating requirements
+ Programming or erasure mechanisms and the conditions that permit or prevent content changes
+ Content retention, read integrity, protection states and hardware replacement constraints
- Firmware algorithms, executable behaviour and software update policy
- ROM image files, software archives and their licensing
- Volatile memory and ordinary RAM made temporarily read-only through access permissions
- General-purpose flash drives, solid-state drives and their storage controllers
- Complete processors, computers or appliances containing ROM
- Detailed semiconductor fabrication processes
Characteristics
- ROM implementation
- mask ROM | one-time programmable ROM | EPROM | EEPROM | flash used as ROM | unresolved Determines whether contents can change and which programming, erasure or replacement actions are physically possible.
- Physical integration
- discrete component | embedded memory region Distinguishes a replaceable part from memory whose service boundary is a larger device.
- Storage capacity and organisation
- bits or bytes, with addressable location count and bits per location Allows an agent to interpret addresses and compare memory requirements without confusing capacity with word width.
- Read interface
- parallel | serial | internal mapped interface | implementation-specific Determines how a host accesses stored values and what interface evidence is required.
- Read timing
- access time in ns or µs; clock rate in Hz where applicable, with operating conditions Determines whether the host can obtain valid data within its timing constraints.
- Electrical operating limits
- supply and signal voltages in V; current in A; separate programming conditions where applicable Prevents incompatible reads or programming attempts and supports power budgeting.
- Programming and protection state
- blank | programmed | partially programmed | write-protected | permanently locked | unknown; applicability depends on implementation Constrains permissible operations and identifies irreversible transitions.
- Retention specification
- specified duration in years with temperature and other qualifying conditions Supports assessment of stored-data longevity without treating nonvolatile storage as permanent.
- Programming endurance
- specified programming or erase cycles; not applicable for non-reprogrammable implementations Constrains repeated changes where supported and avoids assigning rewrite capability to immutable ROM.
- Content verification state
- unread | read successfully | matched trusted reference | mismatch | unstable reads | inaccessible Separates successful electrical access from evidence that the contents are correct.
- Host and content associations
- containing device, mapped region, compatible host revisions and referenced content identity Connects the memory to its intended use without absorbing the host or firmware into this model.
Also called
Where this came from
wikidata · CC0 1.0
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 6 bundles · 11 layers · 16 findings · 30 questions.
ROM identity and boundary Establishes which physical memory the model describes and what read-only means for that implementation.
The term ROM can refer to immutable silicon, specially programmable memory or a stored image; agents must resolve that ambiguity before acting.
Physical memory identity
Identifies the memory component or embedded region independently of its contents.
Component or region boundary
Record whether the ROM is a discrete component or an identifiable region within another device, together with evidence locating it.
- Which physical component or embedded address region is being identified as read-only memory? boundary
- Which marking, device documentation or memory map establishes that identity? provenance
Meaning of read-only
Separates physical immutability from restricted programming and temporary write restrictions.
ROM classification basis
Record the implementation and the basis for treating it as ROM, including any distinction between normal reads and content-changing operations.
- Does read-only mean contents are fixed at manufacture, programmable once or changeable through a separate procedure? definition
- If the storage is EEPROM or flash, what documented role or classification places it within this ROM model? boundary
Content establishment and mutability Describes how bits are initially established and whether they can subsequently change.
An agent must distinguish replacement-only ROM from programmable variants before recommending an update or attempting erasure.
Initial content establishment
Captures manufacture-time or later programming and its verification evidence.
Programming origin
Identify when and by what supported process the contents are established, without assuming every ROM begins as a user-programmable blank.
- Are contents established during manufacture or through a subsequent programming operation? definition
- What programming record or manufacturer identifier connects this memory to its intended content revision? provenance
Permitted content transitions
Defines supported content changes, erase granularity and irreversible states.
Rewrite and lock constraints
Record whether further programming is possible, whether erasure is required and which protection transitions prevent later changes.
- Which documented procedure, equipment and operating conditions permit programming or erasure, if any? action
- What is the affected programming or erase unit, and which operations or locks are irreversible? boundary
- What evidence establishes the present blank, programmed or protected state? provenance
Addressing and read operation Describes how stored locations become valid data at the host interface.
Correct ROM identification is insufficient if an agent reads the wrong addresses, misinterprets organisation or violates interface timing.
Storage organisation
Captures capacity, location width and the mapping between host requests and stored locations.
Address-to-content mapping
Record addressable capacity, word width and any host mapping or banking needed to reconstruct a complete read.
- How many locations are accessible, how many bits does each contain and what capacity does that represent? measurement
- How do host addresses, bank selections or serial commands select the intended stored locations? definition
Valid read conditions
Specifies the interface states and operating limits required for reliable reads.
Electrical and timing contract
Record supply, signalling, selection and timing requirements from documentation applicable to the implementation.
- What supply voltage, signal levels and access timing or clock limits apply under the intended operating conditions? measurement
- Which enable signals, commands or host states are required to read without contention or unintended programming? action
- Which datasheet or interface specification establishes these requirements for this device revision? provenance
Retention and content integrity Separates persistence of stored bits, repeatable reads and correspondence with intended contents.
A ROM can return stable but incorrect contents, while an interface fault can make intact storage appear corrupt.
Retention and wear
Captures applicable retention conditions and programming-related limits.
Qualified storage lifetime
Record retention and endurance claims with their conditions and applicability, leaving undocumented lifetime estimates unresolved.
- What retention duration is specified, and under which temperature and usage conditions? measurement
- For reprogrammable implementations, what endurance limit and programming history are available? provenance
Verification and diagnosis
Establishes what observations support a conclusion about stored-data integrity.
Readback evidence
Distinguish repeatable readback, agreement with a trusted reference and unresolved faults in the memory or read path.
- Do repeated reads under valid operating conditions produce identical data across all accessible locations? measurement
- Which trusted image, digest or manufacturer verification mechanism establishes the expected contents? provenance
- What diagnostic action can distinguish stored-bit errors from addressing, timing, power or connection faults? action
Host integration and service Connects ROM hardware and content identity to compatibility, access restrictions and service decisions.
Matching capacity or package alone does not establish that a ROM can safely replace another or serve the same host function.
Host and content compatibility
Records the host relationships needed to assess functional substitution.
Replacement compatibility
Compare physical and electrical fit, read behaviour and required content revision before treating two ROMs as interchangeable.
- Which package, pinout or embedded interface, capacity and timing requirements must a replacement satisfy? boundary
- Which host revisions require which content identity, and what evidence establishes that association? provenance
Access and service decisions
Determines whether readout, programming or replacement is feasible for the installed memory.
Serviceable action boundary
Record readout restrictions, hardware protection and the smallest replaceable assembly, separating technical capability from permission to act.
- Can this memory be read or programmed in place, or does access require removal, a service mode or a dedicated programmer? action
- If contents cannot be changed or verified, which component or containing assembly is the documented replacement boundary? boundary
- Which protection states and authorisations govern the proposed readout or content-changing operation? action
Evidence and external alignment What the world already says about this thing, gathered so the model can be checked against it.
A model that cannot be lined up against existing standards, identifiers and practice cannot be adopted by anyone who already uses them.
Reported evidence
Findings from the breadth pass, kept separate from the structural claims.
Check these first
Recalled without web access and unsourced; every item is a lead to verify.
- This describes the semiconductor memory category, not a particular chip, firmware image or colloquial use of ROM to mean device storage.
- Terminology varies: strict usage reserves ROM for permanently fixed contents, while broader usage includes PROM, EPROM, EEPROM and flash.
- The measurement ranges are illustrative recall, not verified specifications; retention, access time and capacity require technology-specific datasheets.
- Which of these check these first hold for the sense of read-only memory this model covers, and on what evidence? provenance
Kinds and varieties
Recalled without web access and unsourced; every item is a lead to verify.
- Mask ROM, programmed during manufacture
- Programmable ROM (PROM), programmable once
- Erasable programmable ROM (EPROM), erased using ultraviolet light
- Electrically erasable programmable ROM (EEPROM)
- Flash memory, an electrically erasable form commonly erased in blocks
- Which of these kinds and varieties hold for the sense of read-only memory this model covers, and on what evidence? provenance
Real-world use
Recalled without web access and unsourced; every item is a lead to verify.
- Storing boot code and device firmware
- Holding fixed lookup tables, character generators and control data
- Distributing software in game cartridges
- Retaining configuration and calibration data in electrically programmable variants
- Providing immutable startup or recovery code in embedded processors
- Which of these real-world use hold for the sense of read-only memory this model covers, and on what evidence? provenance
Typical measurements
Recalled without web access and unsourced; every item is a lead to verify.
- Storage capacity in embedded firmware applications - A few kilobytes to tens of megabytes, depending on technology and application - byte
- Parallel ROM read access time - Tens to hundreds of nanoseconds for many discrete devices - ns
- Specified data retention - Often 10-20 years for programmable devices under stated operating conditions - year
- Which of these typical measurements hold for the sense of read-only memory this model covers, and on what evidence? provenance
Failure modes and hazards
Recalled without web access and unsourced; every item is a lead to verify.
- Charge loss in charge-storage variants can corrupt retained bits, particularly with elevated temperature or accumulated wear.
- EEPROM and flash have finite erase/write endurance; exceeding it can cause programming or retention failures.
- Power interruption during electrical programming or erasure can leave firmware incomplete or corrupted.
- Electrostatic discharge, excessive voltage or operation outside temperature limits can damage the device.
- Errors or vulnerabilities in permanently programmed code can require hardware replacement or an external workaround.
- Which of these failure modes and hazards hold for the sense of read-only memory this model covers, and on what evidence? provenance
Neighbouring kinds and how to tell them apart
Recalled without web access and unsourced; every item is a lead to verify.
- Random-access memory (RAM) - RAM ordinarily supports routine reads and writes during computation; ROM restricts modification. Random access itself does not distinguish them, because ROM can also support random addressing.
- Nonvolatile memory - Nonvolatile memory is the broader category of memory that retains data without power; ROM additionally describes fixed or specially programmed contents.
- Flash memory - Flash is an electrically reprogrammable nonvolatile technology often grouped into the ROM family, but it also serves frequently rewritten storage applications.
- Firmware - Firmware is the stored program or control information; ROM is one physical medium that can hold it.
- Read-only storage - Read-only storage includes media and access restrictions beyond semiconductor memory; a writable device made read-only by software is not thereby a ROM device.
- Which of these neighbouring kinds and how to tell them apart hold for the sense of read-only memory this model covers, and on what evidence? provenance
What the second pass must settle
- Does the registry intend ROM in the narrow immutable sense or the broader family that includes EPROM, EEPROM and flash used as ROM?
- Which existing Vercy models cover semiconductor memory, flash memory, firmware and embedded memory regions, and where should this model link to them?
- Which manufacturer documents and issuing-body standards should ground implementation-specific interface, programming and qualification requirements?
- What sourced retention, endurance, capacity and timing ranges are useful for each ROM implementation without implying universal limits?
- Which failure mechanisms and diagnostic procedures are established for each implementation, and what evidence is sufficient to distinguish memory failure from host-interface failure?