diff --git a/bip-XXXX.mediawiki b/bip-XXXX.mediawiki new file mode 100644 index 0000000000..8daf4477c8 --- /dev/null +++ b/bip-XXXX.mediawiki @@ -0,0 +1,43 @@ +
+  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.