Announced at the World Digital Mining Summit in September 2023, the Antminer S21 Series has set the standard for Bitcoin ASIC mining machines. With pre-orders being made in late 2023 and shipments being carried out through the first half of 2024, the S21 Series has changed the landscape of the Bitcoin mining industry.

The series provided marked improvements in efficiency over both previous generations and competitors. While there have been several models since released in the series, the specs of the original S21 machine brought a hashrate of 200 TH/s and an efficiency of 17.5 W/TH to customers. Future models in the series will bring hashrate as high as 860 TH/s and efficiency as low as 12 W/TH, cementing the series as the current industry standard.

At the core of the S21 Series efficiency and hashrate performance is the BM1368 chip. The chip set new benchmarks for hashrate and efficiency by employing advanced parallel processing architecture and innovative heat dissipation to minimize energy loss.

Antminer S21 Architecture

Chip design and fabrication is largely responsible for the power and efficiency which an ASIC can provide. Bitmain has been a longstanding customer of TSMC which has provided them with a competitive edge in their chip fabrication process. TSMC stands at the frontier of fabrication technology producing chips for companies like Apple, AMD, and Nvidia.

The BM1368 chip has provided a significant advancement in mining technology. Each machine integrates three hashboards with 108 chips per hashboard totalling 324 chips per machine. The chips are supported by hardware architecture that optimizes for energy efficiency. The machine features dual aluminum heat sinks along with front and rear fans for enhanced thermal management and more powerful airflow compared to previous generations. The power supply unit, plug type, and control board are also all designed to offer more stable and reliable connectivity.

Since the initial S21 shipments in the first half of 2024, Bitmain has released several other models in the series. The S21 XP hydro provides the most advanced specs of these releases with a hashrate of 473 TH/s and an efficiency of 12 W/TH. However, the entire XP series of the S21 is still only available for preorder with shipments expected in October.

Antminer S21 versus Previous Generations

Officially announced in February 2020, the Antminer S19 Series is the previous generation of Bitmain ASICs. Bitmain collectively announced both the Antminer S19 and the Antminer S19 Pro with the Pro model having a hashrate of 110 TH/s and an efficiency of 29.5 TH/s.

Improvements in chip designs combined with years of research and development by Bitmain have brought significant improvements in the Antminer S21 series compared to the previous generation. The below chart highlights the improvements in the Antminer S21 compared to the Antminer S19 and the further improvements in the specs of the Antminer S21 XP Hydro. Note that the efficiency has been multiplied by a factor of 10 in the below chart for scaling purposes.

Antminer S21 versus WhatsMiner

Founded by former Bitmain engineer Zuoxing Yang, MicroBT has become Bitmain’s only legitimate rival. Prior to MicroBT and their WhatsMiner machine series, the Bitcoin ASIC hardware market was heavily concentrated in the hands of Bitmain with estimates putting Bitmain’s share of the market at roughly 75% in 2017 and likely even higher preceding this.

MicroBT has carved a significant share of the market with their WhatsMiner machines which have become a reliable mining machine for customers. In terms of performance, the WhatsMiner M50 Series closely rivaled the Antminer S19 Series.

However, the Antminer S21 Series has set the standard in terms of machine efficiency. The below graph highlights how the latest-generation of Whatminer machines fare against the Antminer S21 Series in terms of hashrate and efficiency with the upper right of the graph being the optimal area. The only model series which is less efficient than any of the latest generation Whatsminer machines is the Antminer T21 which is a lower-priced but less-powerful variant of the S21.

Antminer S21E XP 3U Announcement

Bitmain has recently announced what will be the latest in the Antminer S21 Series. The Antminer S21E XP 3U model. This machine will have a hashrate of 860TH/s, almost doubling the most powerful current XP model. This will be combined with an efficiency of 13 J/TH.

The machine will be the first to integrate direct liquid-to-chip (DLC) within a U form factor. DLC cooling is a method which involves circulating a liquid coolant directly over the components of the ASIC by utilizing a cold plate. This coolant absorbs heat facilitating efficient heat transfer. The U form factor refers to the shape and size of the equipment with a design to enable easy integration into existing infrastructure.

The announcement of the Antminer S21 XP 3U marks the latest innovation in what has been an extremely disruptive S21 Series. While WhatsMiner machines are certainly a highly competitive ASIC machine, Bitmain has set the standard for efficient hashing with their Antminer S21 Series.