BM1398

BM1398 is Bitmain's 7 nm SHA-256 mining ASIC (silicon chip ID 0x1398), the third-generation die that powers the original Antminer S19 family. Released in 2020, it followed the 7 nm BM1397 of the S17/T17 generation and preceded the 5 nm BM1366 used in the S19 XP. Each BM1398 computes the double-SHA-256 hashes that Bitcoin's proof-of-work depends on, running at roughly 90 GH/s per chip at a factory efficiency near 29.5 J/TH.

Where the BM1398 is used

The BM1398 is the die behind the original Antminer S19 family that defined Bitmain's 2020 product cycle. It powers the base S19 (76 chips per board), the higher-binned S19 Pro (114 chips per board), and the S19j, S19a, and air-cooled T19. A frequently misunderstood point: the S19 and the S19 Pro carry the same BM1398 silicon on the same 38-domain hashboard — the difference is how many chips are populated per domain (two on the S19, three on the S19 Pro), not a different chip.

Note the family split, because "S19" on a spec sheet does not automatically mean BM1398. The later S19j Pro moved to a separate 5 nm die (the BM1362), and the S19 XP stepped up to the BM1366. Only the original S19, S19 Pro, S19j, S19a, and T19 actually carry the BM1398.

What the silicon looks like

A BM1398 is an ASIC chip built on a 7 nm process and hashes at roughly 90 GH/s on its own. On a stock hashboard the chips are wired in a single serial chain and organized into 38 voltage domains, so the control board manages current across small groups of chips rather than one chip at a time. A complete S19 carries three of these boards, putting 228 BM1398 dies (or 342 on an S19 Pro) behind a single miner's nameplate hashrate.

The domain count is the key to telling the two boards apart at the silicon level. On the S19, two chips sit in each of the 38 domains (76 chips total) at roughly 0.36 V per domain, with the board stepping its input rail up from about 14 V to 19 V across the chain. On the S19 Pro, three chips share each domain (114 chips total) at roughly 0.32 V per domain, with the boost topology running from about 12.6 V up to 20 V. Same die, denser population, different rail engineering.

Power, voltage domains, and the PIC controller

Like the rest of its generation, the BM1398 exposes a tunable PLL frequency and per-domain voltage, so custom firmware can walk the chip across operating points to chase efficiency, hashrate, or a target power envelope — the same voltage-domain granularity that makes underclocking an S19 worthwhile. One hardware detail separates this generation from the newer S21 boards: BM1398 hashboards use a dedicated dsPIC33EP voltage controller (a PIC-class microcontroller) to set the domain rails, whereas the later S21 "no-PIC" boards manage voltage with DAC controllers on the I2C bus. If you are servicing an S19, that PIC is part of the diagnostic chain you have to account for.

Why it matters for repairs and buyers

The S19 line is the most-traded used ASIC on the market, which means harvested BM1398 dies and re-worked boards are everywhere. Two checks protect a purchase: confirm the chip count (76 versus 114) before paying a "Pro" premium, and verify the dsPIC33EP voltage controller is the genuine part rather than a substitute. A genuine BM1398 board is dispatch-compatible for repair, but an S19 board and an S19 Pro board are not interchangeable wholesale — they differ in chip population, domain wiring, and boost topology, so always match the board to the model.

For anyone running or repairing this hardware, understanding the BM1398's chain length, 38-domain layout, and tuning headroom is what lets you reason about real-world efficiency and judge whether a low hashrate reading is a tuning issue or a failing chain. To compare the S19 family side by side, see our miner catalog, and to get the most out of the silicon you already own, the firmware comparison lays out how tuning choices turn raw BM1398 hashrate into sustainable, efficient mining.