Older ads still say 840 KSol/s. Bitmain Support figures for the current Z15 Pro typically cite 860 KSol/s (±3%). Either way, a healthy cool unit should not live permanently at 700–800K. Read 860K vs 840K listings for the naming mess, then use this page to recover hash.
First: measure the right things
- Local hashrate after 30+ minutes warm-up
- Pool hashrate (often smoother / delayed)
- Wall watts on a PDU
- Inlet air temperature
- How many hashboards the UI detects
Common causes
Heat and airflow
Recirculated hot air throttles chips. Clear intake/exhaust, separate hot aisle, and avoid sealed cupboards. Noise ~75 dBA class means you need a real space.
Power delivery
One AC cord, long thin extensions, or sagging voltage under load will cut hash. Confirm 200–240 V and dual feeds: power & wiring.
Missing or sick hashboard
If the UI shows fewer boards than expected, you will never hit full rating. Go to hashboard not detected.
Firmware / OC instability
Custom firmware or aggressive tunes can look fast then settle low with errors. Return to official stock (best firmware 2026).
Quick diagnostic order
- Cool the room; re-check after 1 hour.
- Verify both AC cords and PDU watts near ~2780 W class when hashing.
- Confirm all boards detected.
- Stock firmware + known-good Equihash pool.
- Only then suspect individual board hardware.
Watts near stock but hash stuck low points to boards/FW. Hash low and watts low often means the miner is not fully loaded (pool/config) or is power-starved.
Related: Hashboard not detected · 860K vs 840K · All guides