README

MacClassicBitMiner

A real Bitcoin Stratum pool miner for classic Macintosh computers running Mac OS 6.0.8, written in THINK Pascal with an optional hand-written 68000 assembly SHA-256. It builds real block headers, does real double-SHA256, and submits real shares to real pools.

It will not earn meaningful Bitcoin — a Mac Plus does ~20 hashes/second and a modern ASIC does ~100,000,000,000,000. That is the whole point. This is a retro-computing art project that happens to be a technically correct miner.

Status

This is an in-progress revival. The mining logic has been rebuilt from a validated reference implementation and ported into Pascal; it has not yet been recompiled on real hardware (the author's vintage Mac is temporarily down).

If you build it, click Self-Test first — it hashes the genesis block header on your Mac and must display Self-Test: PASS. That single check proves the whole SHA-256d + byte-order pipeline compiled correctly, with no pool required.

What was fixed in this revival

The earlier code looked complete but did not actually mine or compile cleanly. The important fixes:

• It now hashes a real 80-byte block header. The previous loop hashed only 4 bytes of the nonce, so it wasn't mining any real work.
• It parses the actual job. mining.notify is fully decoded (prevhash, coinbase parts, merkle branch, version, nbits, ntime) and the coinbase + merkle root + header are assembled correctly.
• Shares are submitted correctly — real job id, extranonce2, ntime, and a big-endian nonce — so a pool can accept them.
• DNS works. Pool hostnames like solo.ckpool.org are resolved via the MacTCP DNR (numeric IPs also accepted). The old code treated the hostname as a dotted-quad IP and could never connect.
• Compile/logic bugs fixed: the OpenDriver/ioCRefNum MacTCP setup; a SHA-256 word-load that byte-swapped on the (big-endian) 68000 and would have produced wrong hashes; and a case-insensitivity clash between the Pascal Sigma0/sigma0 helpers.
• Long messages no longer truncate — Stratum lines are buffered instead of being forced into a 255-byte string.

Requirements

Hardware: any 68000/68020/68030 Mac, 1 MB RAM recommended, MacTCP installed, a network connection.

Software: Mac OS 6.0.8+, THINK Pascal 4.0+, MacTCP configured with an IP. For DNS you also need Apple's DNR glue (dnr.c, from the MacTCP developer kit) added to the project — or just enter a numeric IP for the pool.

Building

1. Open BitcoinMiner.pas in THINK Pascal.
2. For DNS support, add Apple's DNR glue (dnr.c) to the project. To build without it (numeric-IP pools only), change the line near the top: {$SETC USE_DNR := 1} to {$SETC USE_DNR := 0}.
3. Project → Build, then run.
4. Click Self-Test. It must say Self-Test: PASS.

Optional: assembly speedup (experimental)

sha256.a provides 68000 assembly versions of the SHA-256 helpers. It is unverified on hardware — the Pascal path is the validated default. To try it:

1. Add sha256.a to the project and add {$L sha256.a} to BitcoinMiner.pas.
2. Comment out the seven Pascal functions ROTR, Ch, Maj, BigSigma0, BigSigma1, SmSigma0, SmSigma1 and declare each external instead, e.g. function ROTR(x: LongInt; n: Integer): LongInt; external;.
3. Rebuild and click Self-Test. If it does not say PASS, revert to Pascal.

Usage

1. Launch the miner.
2. Enter:
   • Wallet Address — your Bitcoin address (used as the worker username on solo pools).
   • Pool Address — e.g. stratum+tcp://solo.ckpool.org:3333 (or IP:port).
   • Worker Name and Password (x is typical).
3. Click Connect. Status moves Connecting → Subscribing → Authorizing → Mining, and the hash rate and share counters update live.

Example pools

The reference implementation

reference/ contains the Python ground truth the Pascal was ported from, plus its test suite. Run it with:

python reference/test_reference.py       # crypto + pipeline
python reference/test_pascal_parser.py    # Stratum parser + wiring

It validates SHA-256 against NIST vectors, reconstructs and re-hashes the real Bitcoin genesis block header, checks merkle-branch folding, cross-checks the no-bignum difficulty test against native big integers over 20,000 random cases, and verifies every Stratum field lands in the right slot.

Not yet verified against a live pool: the prevhash word-swap (genesis can't exercise it — its prevhash is zero). If a pool rejects otherwise-valid shares, check that first.

Reality check

You will not make money, find a block, or reach a payout threshold — the numbers are astronomical against you. You will do real SHA-256d, submit real shares, appear on a pool dashboard, and run 2009 cryptocurrency on 1991 hardware.

License

CC0-1.0 (public domain). Experimental/educational software, no warranty.

Acknowledgments

Drewy Nucci for the fever dream; Satoshi Nakamoto for Bitcoin; Apple for the Macintosh; Motorola for the 68000; and everyone who said you can't mine Bitcoin on a Mac Plus.