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[2620:6e:a000:1::99]) by gmr-mx.google.com with ESMTPS id d9443c01a7336-2adfb27c794si1160575ad.1.2026.02.26.14.12.05 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 26 Feb 2026 14:12:05 -0800 (PST) Received-SPF: pass (google.com: domain of lf-lists@mattcorallo.com designates 2620:6e:a000:1::99 as permitted sender) client-ip=2620:6e:a000:1::99; X-DKIM-Note: Keys used to sign are likely public at X-DKIM-Note: https://as397444.net/dkim/mattcorallo.com and X-DKIM-Note: https://as397444.net/dkim/clients.mail.as397444.net X-DKIM-Note: For more info, see https://as397444.net/dkim/ Received: by mail.as397444.net with esmtpsa (TLS1.3) (Exim) (envelope-from ) id 1vvjaW-0000000Aq1r-25i5 for bitcoindev@googlegroups.com; Thu, 26 Feb 2026 22:12:04 +0000 Message-ID: <6fa0cb45-37d6-4b41-9ff8-03730fd96d6e@mattcorallo.com> Date: Thu, 26 Feb 2026 17:12:03 -0500 MIME-Version: 1.0 From: Matt Corallo Subject: [bitcoindev] [BIP Draft] 24 bits for nVersion nonce space instead of 16 To: Bitcoin Development Mailing List Content-Language: en-US Content-Type: text/plain; charset="UTF-8"; format=flowed X-Original-Sender: lf-lists@mattcorallo.com X-Original-Authentication-Results: gmr-mx.google.com; dkim=pass header.i=@mattcorallo.com header.s=1772142062 header.b="Z/n93k3u"; dkim=pass header.i=@clients.mail.as397444.net header.s=1772142064 header.b=WsHzb9oE; spf=pass (google.com: domain of lf-lists@mattcorallo.com designates 2620:6e:a000:1::99 as permitted sender) smtp.mailfrom=lf-lists@mattcorallo.com; dmarc=pass (p=NONE sp=REJECT dis=NONE) header.from=mattcorallo.com Precedence: list Mailing-list: list bitcoindev@googlegroups.com; contact bitcoindev+owners@googlegroups.com List-ID: X-Google-Group-Id: 786775582512 List-Post: , List-Help: , List-Archive: , List-Unsubscribe: , X-Spam-Score: -0.8 (/) 
   BIP: ?
   Title: 24 nVersion bits for general purpose use
   Author: Matt Corallo 
   Status: Draft
   Type: Specification
   Created: 2026-02-26
   License: BSD-3-Clause
            CC0-1.0
   Replaces: 320
==Abstract== 24 bits are reserved in the nVersion field as extra nonce space for miners, providing for additional hashrate with header-only mining without relying on rolling nTime more often than once per second. ==Motivation== BIP 320 defined 16 bits of nVersion as nonce space for additional nonce space. It turns out that this isn't enough, as some devices have started using 7 bits from nTime for extra nonce space (see https://github.com/stratum-mining/sv2-spec/discussions/187). Given there's limited utility in 16 bits of nVersion space for signaling, instead here we offer 24 bits of nVersion space as extra nonce space. ==Specification== 24 bits from the block header nVersion field, starting from 5 and ending at 28 inclusive (0x1fffffe0), are reserved for nonce use and removed from BIP8 and BIP9 specifications. A mask of 0xe000001f should be applied to nVersion bits so bits 5-28 inclusive will be ignored for soft-fork signalling and unknown soft-fork warnings. ==Rationale== Headers-only mining avoids mining devices (either ASICs or the firmware) from having to concern itself with the vast space of consensus logic (handling transactions, merkle trees, etc). It is widely deployed in ASICs, but requires a substantial number of jobs fed across an entire device, keeping the ASIC controller busy. Providing additional nonce space for the ASICs to roll without needing fresh work from the controller may simplify ASIC design somewhat, and as been apparently adopted in some miners by using extra space in nTime as extra nonce space. Doing so in nVersion instead is preferable to using nTime. ==Backwards Compatibility== Non-upgraded nodes will interpret the reserved bits of this proposal as signals for soft forks, and may additionally activate the warning system for unknown soft forks. At the time of writing no known soft forks are pending using any of 24 bits reserved in this BIP, and given that a non-trivial percentage of the hashrate is already making uses of those bits, future soft forks SHOULD NOT utilize those bits for activation signalling. ==Acknowledgements== Timo Hanke and Sergio Lerner for originally proposing 15-bit extra nNonce2. Btc Drak for writing BIP 320. ==Changelog== ==Copyright== This document is dual licensed as BSD 3-clause, and Creative Commons CC0 1.0 Universal. -- You received this message because you are subscribed to the Google Groups "Bitcoin Development Mailing List" group. To unsubscribe from this group and stop receiving emails from it, send an email to bitcoindev+unsubscribe@googlegroups.com. To view this discussion visit https://groups.google.com/d/msgid/bitcoindev/6fa0cb45-37d6-4b41-9ff8-03730fd96d6e%40mattcorallo.com.