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Tonolith v1 ROM and commitment layout

Tonolith v1 uses one immutable, content-addressed ROM tree per CPU instance. The ROM is not copied into mutable execution state. Its root cell is stored in the contract data and is bound to staticCommitment at deployment.

Addressing

  • 1,024 words;
  • one word is 16 bits;
  • a ROM address is uint10, 0..1023;
  • words are assembled and stored in ascending address order;
  • a word is canonical only when its opcode-specific operand width is valid.

The tree is four-way at every level:

RomRoot
├── level20: 16-leaf half
│   ├── level10..level13
│   │   └── leaf0..leaf3
├── level21: 16-leaf half
│   ├── level10..level13
│   │   └── leaf0..leaf3
├── level22: canonical zero subtree
└── level23: canonical zero subtree

There are 32 leaves. Each RomLeaf contains 32 words as two fixed-width fields:

firstHalf:  uint256  // words leaf*32 + 0 .. +15, big-endian within the field
secondHalf: uint256  // words leaf*32 +16 .. +31, big-endian within the field

The two unused root children remain canonical zero subtrees. The TypeScript ROM builder constructs those zero subtrees independently; it must not reuse a program-bearing level-2 node as a zero node.

RAM packing

RAM contains 256 nibbles. It is four RamPage cells, each a uint256 holding 64 nibbles. Address page * 64 + offset is stored at bit range offset * 4 .. offset * 4 + 3 (least-significant nibble first). The TypeScript ramRootCell and the Tolk readRamNibble/writeRamNibble functions use the same packing.

Static commitment

The commitment is the hash of one fixed-width cell:

uint32  namespace    = 0x544E4C01
uint16  schema       = 1
uint16  ISA          = 1
uint256 romRootHash

This is a binding to the complete ROM root hash, not a proof that a particular instruction was produced by a gate-level or Intel 4004 implementation. The contract recomputes and checks the commitment before every accepted Advance.

Fibonacci v1 vector

The assembled program in programs/fibonacci.tasm has 21 words. Its expected commitments are:

ROM root:          029ccf15774f680518705bb7c8be4b2ca92f34a4ceb9c963e55609225398c748
static commitment: 50da71fe389768e885c8258c7f4f4a97b86598738eed974336d527e459024f08

These values are checked by the TypeScript ROM tests and are used by the Tolk Fibonacci contract test and the testnet deployment script.