# tt_expected_chip_count

[<< Home](../index.md) | [<< Metrics](../metrics.md)

## Name

### Prometheus Metric Name

```
tt_expected_chip_count
```

### Metric Path (tt-telemetry)

Schema:

```
{hostname}/tt_expected_chip_count
```

Example path:

```
wh-glx-c12u04/tt_expected_chip_count
```

## Description

The number of Tenstorrent chips a Galaxy host is expected to expose. This is a fixed reference value used alongside [tt_chip_count](tt_chip_count.md) to detect a mismatch between what the host should have and what UMD currently sees on the PCI bus.

The metric is created only when the host is identified as a Galaxy system. This identification is made from the Factory System Descriptor (FSD): the host is a Galaxy if the FSD lists a board location for it with board type `UBB` (Wormhole Galaxy) or `UBB_BLACKHOLE` (Blackhole Galaxy). Because this check reads the FSD rather than the device, **the metric is only available when a valid FSD that includes this host is provided** — if no FSD is configured, or the host is absent from it, the metric is not emitted (even on a Galaxy machine). On non-Galaxy hosts the metric is likewise not emitted.

The value is set once at metric creation to `32`. It is not refreshed on later collection cycles. 

On creation, if the live [tt_chip_count](tt_chip_count.md) differs from the expected value, tt-telemetry logs an error (`Chip count mismatch`).

## Values

**Type:** Unsigned Integer

**Units:** None

**Allowable values:** `32` on Galaxy hosts. The value is constant for the lifetime of the collector process after the metric is first created.

## Related Metrics

|Metric|Description|
|---|---|
|[tt_chip_count](tt_chip_count.md)|Observed chip count from PCI device enumeration; compare against `tt_expected_chip_count` on Galaxy hosts.|
|[tt_driver_initialized](tt_driver_initialized.md)|Whether the device driver is initialized. Note that `tt_expected_chip_count` is independent of whether the driver initializes successfully.|

## Prometheus Labels

|Label Name|Value|
|---|---|
|hostname|The host from which the metric was collected.|
|hall|The datacenter hall where the host is located. Sourced from the Factory System Descriptor (FSD).|
|aisle|The datacenter aisle where the host is located. Sourced from the Factory System Descriptor (FSD).|
|rack|The rack number where the host is located. Sourced from the Factory System Descriptor (FSD).|
|shelf_u|The shelf U position in the rack where the host is located. Sourced from the Factory System Descriptor (FSD).|