Hash Board Slots, Heatsinks and Screws on Whatsminer and Antminer

An error code names a slot. Before you pull a board, that slot has to map to a physical position in the chassis — and the mapping is not the same on a Whatsminer as on an Antminer, nor the same across Antminer control boards. Once the board is out, the heatsinks and screws have rules of their own. This guide covers both.

Whatsminer slots: SM0, SM1, SM2

A typical air-cooled Whatsminer has three hash-board slots, numbered SM0, SM1 and SM2. Stand at the air-intake side — the fan-grille end — and look in: SM0 is on the right, SM1 in the centre, SM2 on the left.

• The order is fixed by the physical layout of the transfer board. It is not configurable and does not depend on how anything is cabled.
• Error codes reference the slot number, so a code against SM2 means the left-hand board as seen from the intake side. MicroBT's error-code reference is on its support page.
• Some models ship with only two physical boards. The numbering still follows the same pattern.

Antminer slots and cable channels

An air-cooled Antminer also has three hash-board slots, but the board number in the miner's interface is not set by where the board sits in the chassis. It is set by which connector on the control board its data cable is plugged into. Those connectors are the channels, CH0 through CH3, and a control board has three or four of them depending on which platform it is. The interface lists boards as 1, 2, 3 and 4; those correspond to CH0, CH1, CH2 and CH3.

So two things determine the board order: the control board fitted, and how the cables were routed. The catch is that on the four-connector boards the channels are not laid out in reading order:

Heatsinks

Whatsminer: one row of screws or two

Whatsminer top heatsinks come in two variants, and you can tell them apart at a glance: Variant 1 is held down by two rows of screws, Variant 2 by a single row. Which one a board uses follows from the number of chips per domain — the heatsink has to sit over the domain layout underneath it.

Antminer: older and updated designs

Older Antminer boards — and the S19k Pro as well — use individual finned heatsinks over each chip. The updated design uses large flat heatsinks spanning the board. The differences are more than cosmetic:

• The newer design moves heat away from the chips more effectively, so the board runs cooler.
• The top heatsink area has been extended while the bottom heatsink is slightly slimmer.
• As on Whatsminer, the number of screw rows holding the top heatsink depends on the chips per domain.

Never mix top heatsinks between boards

Top heatsinks are matched to a particular board — sometimes only lengthwise, which is exactly why a wrong one can look right. During a large batch repair it is easy to put board A's heatsink back on board B: the screw holes line up and everything seats. But a heatsink that is a fraction short leaves the exhaust-side ASICs partly uncovered, and those chips run without adequate cooling.

You will see it in the miner's API log: the affected chips are the ones at the exhaust end of the board, and they will be the ones reporting trouble. Keep each board's top heatsinks with that board, and label them if the boards leave the bench together.

Screws and spacers

Heatsink screws come in two shaft types, thick and narrow, across the M3-, M5- and M6-series sizes the slides note as M3X, M5X and M6X. Some units ship with the long narrow-thread shaft only. The heatsink's own screw holes act as the guide: the hole tells you which shaft it takes, so if a screw does not go in cleanly, it is the wrong screw, not a tight hole.

Antminer aluminum boards come with plastic spacers under the plate-fixing screws — the screws that clamp the positive and negative copper strips. Those spacers insulate the strips from the plate. Do not lose them. A board reassembled without its spacers can stop working or short out.

Reading a slot error and not sure which board it is?

Send us the model, the control board type if you know it, and the error text, and we will tell you which physical board to pull. If it turns out to need bench work, we repair Whatsminer and Antminer hash boards in Chicago — contact us.