How we test every Bitmain S21 Pro before it leaves the shelf

You can buy an S21 Pro from a dozen sellers. The price differences usually come down to two things: where the unit ships from, and what happens to it between landing in inventory and shipping out the door.

Here's exactly what we do.

Step 1: Visual inspection on arrival

When a pallet lands from the manufacturer, every unit gets uncrated and inspected before it goes to the rack. We check:

• Box seal intact, manufacturer tape unbroken, no signs of customs re-tape
• Serial number on the unit matches the box label and the manufacturer's shipment manifest
• Fans spin freely, no transit damage to grilles or housing
• Hashboards seated correctly, no shifted heatsinks
• Power supply cable and accessories present

Anything that fails at this stage goes back to the manufacturer. Not to a different shelf, not to a discount bin, back. Buyers don't see those units.

Step 2: Bench power-up

Before a unit is shippable, it gets a bench power-up test. We connect it to a test PSU, point it at our test pool address, and watch it boot. The test confirms:

• It powers on. Sounds basic, but DOA-on-arrival is the single most common defect, and catching it here saves you and us a return cycle.
• It reaches the login screen. Web UI responds, firmware version is the current manufacturer release, network port detects a cable.
• It accepts pool credentials. The unit can connect to a stratum endpoint and start submitting shares within roughly 90 seconds of boot.
• All hashboards report online. S21 Pros run three hashboards. If one shows as offline in the web UI on first boot, the unit gets pulled and re-seated by a technician before re-test.
• Hashrate ramps to spec within 10 minutes. S21 Pro spec is 234 TH/s ± 3%. If we see a unit climb only to 215 and stay there, it's out of spec and doesn't ship.

Step 3: Firmware verification

We do not ship units with modified firmware. The miner you receive runs the manufacturer's stock firmware build that was current on the day it left our facility. If you want to flash a third-party tune (LuxOS, Vnish, etc.) you do that on your end after delivery.

This is a deliberate choice. Modified firmware voids the manufacturer warranty on most platforms, and a unit that arrives with custom firmware pre-installed gives you no clean baseline to compare against if something goes wrong. We'd rather ship you a known-stock unit and let you make your own firmware decisions.

Step 4: Cool-down, repack, dispatch label

After the bench test, the unit cools, gets repacked in its original manufacturer carton with the original foam inserts, and a reinforced outer box. Pre-shipment photo gets logged against the order. Courier label goes on. Done.

What we won't do

We won't run a 24-hour burn-in test before shipping. Two reasons. First, that's your test, you need to validate the unit in your facility under your ambient conditions, against your power infrastructure, on your pool. Our 10-minute bench test catches the manufacturing defects; the 24-hour burn-in catches the deployment defects, and those are environment-dependent. Second, putting a unit through 24 hours of mining before dispatch ages it slightly, and you're paying for a new unit.

What you get instead is a 60-day written replacement warranty. If a unit fails in normal operation within 60 days, we replace it. That's the right place to handle deployment-stage failures, not in a pre-ship test that delays your dispatch by a day.

Same process for refurbished units

Refurbished S21 Pros (and every other refurbished SKU we sell) go through the same Step 2 bench test, plus an extra cosmetic grading step. Refurb units are visibly graded A/B and priced accordingly. You see the photos of the actual unit before you pay.

If you want to see it

If you're placing a first order with us and want to see your specific unit's bench-test screenshot before dispatch, just ask. We'll send it. Bulk buyers get this by default; retail buyers get it on request.

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