Initially, there was only a CPU for Bitcoin mining, then a GPU. Later, Mighty Asic appeared in 2013, and with this, the form factor for the “shoebox” symbolizing the Bitcoin mining industry appeared.
What’s coming next? Does the shoebox design last as a standard for Bitcoin Mining ASICS? Or will another form factor that resembles a traditional data center server win?
ASIC makers are increasingly betting on the latter – or at least betting that server rack designs for underwater cooling will become a significant part of the Bitcoin mining fleet. Additionally, they are leaning towards cooling “directly to the chip” for even more efficient improvements.
Auradine’s new AH3880 was released in March 2025.
Last September, Bitmain unveiled the U3S21Expph (a little mouthful, eh?) model developed in partnership with the Hut 8. Its U3 design means that one unit takes up three spaces in a traditional server rack. Microbt soon followed with the M63 Hydro series, as did Bitdeer’s Sealminer A2 Hydro unit.
Following the suit, Auradine released the server rack model, the AH3880 this March. The U2 design occupying two server slots is a bit smaller, but packs the hashrate per unit per space at 600 th/s (or 300 th/s per slot) for Bitmain’s 860 Th/s (286.66 th/s per slot).
Shoes out
So, what about the switch from a traditional shoebox? For Aurazine, it’s all about customer demand.
“(Our new model) is based on a lot of feedback we have received from miner clients… We have been working with miners throughout the design process,” Auradine CSO Sanjay Gupta said in his latest mining pod. “They showed us that they were looking for a high-quality hydro-based miner.”
In its partnership with Bitmain for U3S21Expph, “Hut 8 contributed to custom designs for the infrastructure, particularly the U-form factor compatible with HPC-style architecture,” Hut 8 investor relations head Sue Ennis told Blockspacelast in September. (More details on high performance computing angles later).
The advantage of server rack ASICs is their standardization. According to data center developer Cyrus One, Bitcoin Miners are increasingly marching in stages with the traditional data center industry, allowing them to adopt 40% of direct liquid-to-chip cooling by 2026.
If miners adopt this design, supply chains can be optimized by converging on server designs that are theoretically best practices in the major boy data center sector.
This makes buildings and repairs to Bitcoin mines easier. It can also make mining companies more agile if you want to succumb to Bitcoin mining and other forms of computing.
Enter AI and HPC
Like so many mining news today, of course, the ghost of AI is looming in the background.
If miners build data centers using traditional server rack designs, then they want to modify these sites for AI and HPC loads, one less problem is. Of course, they still need to enhance the muscles, muscles and veins of the operation using more robust networking and electrical infrastructure, but server racks provide the backbone of AI/HPC services that require less restructuring than legacy Bitcoin mines. As Ennis said, “The u form factor is… compatible with HPC style architectures.”
To reflect this, Gupta told us in an interview with our Mining Pod, “(The U-form factor) is used in AI data centers. It’s easy to adjust. It also has a high (power) density in AI data centers.
Who is buying it?
Needless to say, Bitcoin mining’s server rack form factor is still in its early stages and is promised that such a design could win, but there is no guarantee.
First, Bitcoin miners need to rewire the interior of the mine as well as completely rewiring the electrical infrastructure (which is unlikely to happen in existing mines).
Brad Cuddy of Cholla, who runs a water-cooled ASIC miner, told Blockspace last September that he was “thrilled to see the transition from Shoebox Design to the (server rack) form factor.” However, he said the voltage range of the U3S21Expph is not compatible with the specific electrical infrastructure used by miners in other Bitmain models.
“The limited range of 380-415 volts reduces compatibility with the modifications. It allowed the voltage range to reach up to 480 volts, allowing for greater interoperability with current infrastructure deployments,” he said.
So it’s possible that miners will see these units integrated into new sites. HUT 8 is taking this approach in its plan to host 15 EH/s for U3S21EXPH units for Bitmain at its Vega, Texas site.
So far, the Hut 8 is the only public buyer of Bitmain’s U3S21Expph. Gupta did not disclose which miners have contracts for AH3880, but he said it includes several industrial-scale private and public miners. It’s no surprise to see Mara, one of Auradine’s key partners, investing more than $50 million in the company.
Assuming that Hut 8’s Vega site runs smoothly on Bitmain’s model and Mara deploys the Aurazine deployment, public miners could lead where others follow, allowing new form factors to slowly penetrate modern mining designs.
