Multi-Algorithm

5 Algorithms, catering for ASIC, GPU and CPU mining:

SHA256d
Two rounds of the SHA256d hashing algorithm, first used by the pioneer cryptocurrency Bitcoin.
Scrypt
Designed to be a CPU-only password hashing algorithm, now mined with ASICs on many altcoins, starting with Litecoin.
Myr-Groestl
A Myriad-specific variant of the Groestl hash algorithm, one of the five finalists in the NIST SHA-3 hash competition.
Skein
Another of the five finalists in the NIST SHA-3 hash competition, first used by Skeincoin.
Yescrypt
CPU friendly, currently GPU resistant. Requires rapid random reads, typically from CPU L1 data cache.
(Retired Algorithm, no longer accepting blocks) Qubit
Originally a CPU-only algorithm, Qubit combines 5 competitors in the NIST SHA-3 hash competition - Luffa, Cubehash, SHAvite, SIMD and ECHO.

Merge Mining

Since block 1402000, merge mining has been allowed on the SHA256d and Scrypt algorithms. This has enabled Myriad to take advantage of the huge hashrates currently in use by coins using these algorithms, further securing the Myriad blockchain.

Merge Mining, or AuxPow, allows the work being done for a parent coin (such as Bitcoin or Litecoin) to be used to find valid blocks on Myriad's blockchain, with no extra load or performance impact to the parent coin.

Distribution

Myriad was released to the wild on February 23, 2014 at 18:30 UTC. The first mined block came 4 minutes later, thus establishing that there was no premine.

The initial reward was 1,000 MYR, halving every 967,680 blocks (approximately 48 weeks). Total supply is approximately 2 billion MYR.

Initially, the target blocktime was 30 seconds, or 150 seconds per algorithm. On the 12th of July, 2015, the community decided to increase the target block time to 60 seconds, or 300 seconds per algorithm, effective at block 1,401,001. At the time, Myriad suffered from low hash rate and extensive difficulty hopping on Scrypt and SHA256d, causing the actual average block time to be over 50 seconds. In addition to enabling aux-PoW on Scrypt and SHA256d, the increase in target block time lead to greater consistency on the network, without affecting fairness of distribution.

Myriad's History

Myriad was launched in February 2014 by 8bitcoder, forked from Zetacoin. It was the first cryptocurrency to use five proof-of-work algorithms in an effort to increase security as well as broaden the base of people who could mine it - SHA256d and Scrypt for ASIC miners, Skein and Myr-Groestl for GPU miners, and Qubit for GPU and CPU miners. Qubit has since been replaced with Yescrypt. Huntercoin, launched in late 2013, was actually the first coin to use multiple PoW algorithms (SHA256d and Scrypt), but its focus was not on mining, rather on a blockchain-based game that produced the large majority of new coins.

Myriad has been mentioned in 'Mastering Bitcoin', first edition, 2014 by Andreas Antonopoulos.

Myriad has spawned several spin-offs, the first of which was Saffroncoin, also utilizing five PoW algorithms. Digitalcoin and Digibyte both hard-forked to use three and five PoW algorithms, respectively. Unitus is another five-algo PoW coin that shares several PoW algos with Myriad, and allows users to merge-mine on all five of its algos. Auroracoin and Verge have also announced plans to fork to multi-algo.

In August 2015 Myriad hard-forked to allow merge-mining on its SHA256d and Scrypt algorithms in an effort to improve security and achieve a more stable hashrate on those two algorithms. At this time the target block time for each algorithm was also changed to five minutes (previously 2.5 minutes), to achieve an overall block target time of 1 minute (previously 30 seconds); this change will stretch the emission curve out by a factor of 2x, to approximately 20 years.

In August 2016, at block 1764000, Myriad used mining consensus to replace the Qubit algorithm with the Yescrypt algorithm to preserve mining decentralization. Myriad became the first cryptocurrency to use mining consensus to change a mining algorithm.