The cryptocurrency market entered the final week of October 2017 with a distinctly different energy than just months prior. While Bitcoin held firm above $6,150 after its historic run past $6,000, the real story was unfolding across the altcoin landscape — fueled in large part by Ethereum’s successful Byzantium hard fork and growing anticipation around the looming SegWit2x upgrade.
TL;DR
- Ethereum’s Byzantium hard fork activated successfully on October 16 at block 4,370,000, implementing nine key protocol upgrades
- ETH traded at $305 with a $29.1 billion market cap, holding strong as the second-largest cryptocurrency
- Bitcoin Cash surged 35.3% in a week to $451.92, leading altcoin gains
- Cardano’s ADA token jumped 10.41% as investor interest in alternative platforms grew
- The upcoming SegWit2x fork drove capital rotation from Bitcoin into major altcoins
Byzantium: Ethereum’s Most Significant Upgrade Yet
Two weeks before October 29, Ethereum executed its Byzantium hard fork at block 4,370,000 — the first phase of the broader Metropolis upgrade. The fork activated at approximately 05:22 UTC on October 16, and it represented one of the most consequential protocol changes in Ethereum’s short history.
Byzantium introduced nine Ethereum Improvement Proposals (EIPs) that collectively enhanced the network’s functionality, privacy capabilities, and long-term sustainability. Among the most notable changes were the introduction of zk-SNARK proofs — the same zero-knowledge cryptography pioneered by Zcash — which opened the door to privacy-preserving smart contracts on Ethereum for the first time.
The upgrade also reduced the block mining reward from 5 ETH to 3 ETH, a deflationary measure designed to slow the growth of Ethereum’s circulating supply. Additionally, Byzantium delayed the so-called “difficulty bomb” — a mechanism intended to eventually force the network toward proof-of-stake — by approximately 18 months, giving developers more breathing room to build the Casper consensus mechanism.
Other technical improvements included optimized gas costs for certain operations, enhanced smart contract security through the REVERT opcode, and improved cryptographic primitives that would support layer-2 scaling solutions down the line.
Altcoin Market Responds With Broad Gains
The successful execution of Byzantium appeared to validate investor confidence not just in Ethereum, but across the broader altcoin market. As of October 29, CoinMarketCap data showed a total cryptocurrency market capitalization approaching $180 billion, with several alternative assets posting impressive weekly gains.
Bitcoin Cash led the charge among large-cap alternatives, surging 35.3% over seven days to reach $451.92. The forked cryptocurrency, which split from Bitcoin in August 2017, benefited from renewed attention as traders positioned themselves ahead of the SegWit2x fork scheduled for November. With a market cap of $7.57 billion, BCH was firmly the fourth-largest digital asset.
Cardano’s ADA token was another standout performer, climbing 10.41% to $0.0286. The nascent smart contract platform, which had only launched its mainnet weeks earlier, was rapidly attracting speculative interest from investors looking for the “next Ethereum.” Its market cap stood at $741 million — small but growing fast.
Among privacy coins, Dash traded at $283.93 with a modest 2.65% daily gain, while Monero held steady at $88.65. Zcash, which had seen significant volatility since its 2016 launch, traded at $234.33 with a 10.45% weekly gain — likely benefiting from the attention Byzantium’s zk-SNARK integration brought to zero-knowledge cryptography.
The SegWit2x Factor
Perhaps the single largest driver of altcoin momentum in late October was the impending SegWit2x hard fork, scheduled for mid-November. The controversial upgrade aimed to double Bitcoin’s block size from 1MB to 2MB, but it faced significant opposition from segments of the Bitcoin community.
This uncertainty created a peculiar dynamic: while Bitcoin itself remained expensive at over $6,150, many traders began rotating capital into altcoins as a hedge against potential Bitcoin volatility. The logic was straightforward — if the fork caused disruption, alternative cryptocurrencies with independent consensus mechanisms would be insulated from the fallout.
Bitcoin had first broken through $6,000 on October 20, and by October 29 it was consolidating around $6,153.85 with a staggering $102.5 billion market cap. Its 24-hour trading volume of $2.86 billion underscored the immense liquidity flowing through the market. Yet the altcoin rally suggested that capital was diversifying, not concentrating.
Emerging Platforms Gain Traction
Beyond the top-ten cryptocurrencies, October 2017 marked a period of growing interest in emerging blockchain platforms. NEO, often called the “Chinese Ethereum,” traded at $27.76 with a $1.8 billion market cap, while Qtum — which combined Bitcoin’s UTXO model with Ethereum’s virtual machine — sat at $10.42.
IOTA, the feeless distributed ledger designed for the Internet of Things, traded at $0.40 with a $1.12 billion valuation. OmiseGO, the Ethereum-based payments platform backed by significant venture capital, held at $7.29. These projects represented a new wave of specialized blockchains moving beyond simple currency use cases.
Even Litecoin, the legacy silver to Bitcoin’s gold, was quietly performing well at $57.11 with a $3.06 billion market cap and 4.47% daily gains — proof that established altcoins still commanded respect alongside the newer entrants.
Why This Matters
The altcoin landscape of late October 2017 represented a pivotal moment in cryptocurrency history. Ethereum’s Byzantium upgrade proved that major blockchain networks could execute complex hard forks without disrupting markets — building confidence that would prove essential as the industry scaled. The combination of technical progress on Ethereum, uncertainty around Bitcoin’s governance, and growing mainstream awareness created ideal conditions for altcoin expansion. Within weeks, this momentum would accelerate dramatically as Bitcoin surged past $7,000 and eventually $10,000, but the seeds of the broader altcoin rally were planted during these October weeks when the market was still digesting what Byzantium meant for the future of smart contract platforms.
Disclaimer: This article is for informational purposes only and does not constitute financial advice. Cryptocurrency markets are highly volatile. Always conduct your own research before making investment decisions.
byzantium was smooth, nine protocol upgrades and barely a hiccup. the eth team was executing well while btc was fighting the segwit2x civil war
Boris D. byzantium implemented metropolis part 1 and the gas refund changes alone made a ton of contracts cheaper to run. technical execution was clean
Boris D. segwit2x was the real catalyst for alt season that month. billions rotated out of BTC into BCH and ADA purely on fork fear. the market was pricing in a chain split
bch up 35% in a week and ada up 10% while btc consolidated. classic capital rotation ahead of a fork. we saw the same pattern repeat in later cycles
segwit2x fears drove so much money into alts that month. people forget how real the split concern was. exchanges were literally preparing for two chain tickers
^ coinbase even announced they would support both chains. turned out to be much ado about nothing but the uncertainty was real
fork_diet_ coinbase also suspended BCH trading right after listing it. the whole period was chaos behind the scenes
Inge P. exchanges preparing two tickers for SegWit2x was real. I remember Bitfinex listing BC1 and BC2 futures. the split never happened but the market traded it like it would
fork_rewind_ Bitfinex listing BC1 and BC2 futures was peak crypto. they were literally creating derivatives for a chain split that was settled in a group chat
ETH at $305 with a $29B market cap post-byzantium. that was the calm before the $1400 storm in january
eth_historian_ and people wonder why eth maxis existed. going from $305 to $1400 in under 3 months will do that to you
eth_historian_ $305 to $1400 in under 3 months after byzantium. metropolis part 2 plus the ICO frenzy was the perfect storm
ETH at 305 with a 29B market cap during Byzantium. feels like looking at a fossil now. the metropolis upgrade was the foundation for everything
Sigrun D. calling 305 a fossil when most alts would kill for those numbers in 2026. byzantium actually shipped on time which is rare for ETH
ETH at 305 with a 29B mcap and people thought it was expensive. those were the cheapest ETH ever priced in human history looking back
segwit2x was the last time miners had real power over protocol decisions. after it failed the pendulum swung hard toward developer governance
Anika R. SegWit2x really was the last gasp of miner governance. after it failed developers controlled the roadmap and never gave that power back
meta_op_ SegWit2x really was the last gasp of miner governance. after that failure developers took the wheel and miners never got it back
ETH at $305 with a $29B market cap during Byzantium. feels like a different universe compared to where it ended up. the metropolis upgrade was genuinely foundational though
Pavel M. byzantium was the foundation but the gas refund mechanism in EIP-3529 later removed half of what it introduced. funny how the upgrades get patched out over time
metropolis_nerd EIP-3529 removing gas refunds wasnt removing a feature it was fixing an incentive bug. contracts were deliberately bloating state to farm refunds
BCH surging 35% that week was pure SegWit2x speculation capital rotating. everyone thought the chain would split and positioned accordingly. classic frontrun
BCH pumping 35% that week was pure speculation on a chain split that never materialized. capital rotating on a narrative not fundamentals, classic 2017
Greta W. BCH surged 35pct on pure speculation and then bled out for years. 2017 was peak narrative trading, zero fundamentals required
byzantium implementing nine EIPs without a single chain split. compare that to the constant testnet disasters we see on modern L2s