What is Bitcoin Cash
The Bitcoin scalability debate led to the cryptocurrency split on August 1, 2017.A chain coming out of the split and setting its block size limit to eight megabytes to increase the number of transactions its ledger can process is called Bitcoin Cash (BCH). The rule change increasing the bitcoin block size limit of one megabyte to eight megabytes is classified as a hard fork. On July 20, 2017 Bitcoin Improvement Proposal (BIP) 91, aka Segregated Witness, activated.
Some members of the bitcoin community felt that adopting BIP 91 without increasing the block-size limit would simply delay confronting the bitcoin scalability problem and that it favored people who wanted to treat bitcoin as a digital investment rather than as a transactional currency.
The plan to do a hard fork was first announced by Bitmain. The project was originally referred to as UAHF: A contingency plan against UASF (BIP148) by Bitmain on their corporate blog, which the ASIC bitcoin mining hardware manufacturer would launch if BIP 148 (a User Activated Soft Fork) succeeded. Subsequently, developers took interest in the project. The Bitcoin Cash name was originally proposed by Chinese mining pool ViaBTC.
The first implementation of the Bitcoin Cash protocol called Bitcoin ABC was revealed by Amaury "Deadal Nix" Séchet at the Future of Bitcoin conference in Arnhem, Netherlands. The Bitcoin Cash hard fork was announced to take place on August 1, 2017.
Upon launch, Bitcoin Cash inherited the transaction history of the bitcoin cryptocurrency on that date, but all later transactions were separate. Block 478558 was the last common block and thus the first Bitcoin Cash block was 478559. Bitcoin Cash cryptocurrency wallet started to reject BTC block and BTC transactions since 13:20 UTC, August 1, 2017 because it used a timer to initiate a fork. It implements a block size increase to 8 MB. One exchange started Bitcoin Cash futures trading at 0.5 BTC on July 23; the futures dropped to 0.1 BTC by July 30. Market cap appeared since 23:15 UTC, August 1, 2017
Move of hashpower and change to difficulty
On August 9, it was 30% more profitable to mine on the original chain. Due to the new Emergency Difficulty Adjustment (EDA) algorithm used by Bitcoin Cash, mining difficulty has fluctuated rapidly, and the most profitable chain to mine has thus switched repeatedly between Bitcoin Cash and mainline bitcoin. As both chains use the same proof-of-work algorithm, miners can easily move their hashpower between the two. As of August 30, 2017 around 1,500 more blocks were mined on the Bitcoin Cash chain than on the original one as the high profitability periods attracted a significant proportion of total processing power.
A fix for these difficulty/hashrate/profitability fluctuations was introduced on November 13, 2:06PM UTC. The EDA algorithm has been replaced with a new difficulty adjustment algorithm (DAA) that hopes to prevent extreme fluctuations in difficulty while still allowing Bitcoin Cash to adapt to hashrate changes faster than mainline bitcoin.