# Form `DCBZ` — DCBZ — Cache Block Zeroing (special X variant)

## Bit Layout

| Bits | Field | Meaning |
| --- | --- | --- |
| 0–5 | `OPCD` | primary opcode (31) |
| 6–10 | `—` | reserved |
| 11–15 | `RA` | base register (0 ⇒ literal 0) |
| 16–20 | `RB` | offset register |
| 21–30 | `XO` | extended opcode (1014 for dcbz / 1010 for dcbz128) |
| 31 | `—` | reserved |

## Instructions Using This Form

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| Mnemonic | Opcode | Group | Description |
| --- | --- | --- | --- |
| [`dcbz`](../memory/dcbz.md) | `0x7c0007ec` | memory | Data Cache Block Clear to Zero |
| [`dcbz128`](../memory/dcbz.md) | `0x7c2007ec` | memory | Data Cache Block Clear to Zero 128 |

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