---
title: "affinity64 Input-Output mask (server configuration option)"
description: Learn about the affinity64 I/O mask option. See when to use it to bind SQL Server disk I/O to a specified subset of CPUs.
author: rwestMSFT
ms.author: randolphwest
ms.date: "03/02/2017"
ms.service: sql
ms.subservice: configuration
ms.topic: conceptual
helpviewer_keywords:
  - "processor affinity [SQL Server]"
  - "binding processors [SQL Server]"
  - "affinity64 I/O mask option"
---
# affinity64 Input-Output mask (server configuration option)
 [!INCLUDE [SQL Server](../../includes/applies-to-version/sqlserver.md)]

  The **affinity64 I/O mask** binds [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] disk I/O to a specified subset of CPUs, similar to the **affinity I/O mask** option. Use **affinity I/O mask** to bind the first 32 processors, and use **affinity64 I/O mask** to bind the remaining processors on the computer. If you reconfigure the **affinity64 I/O mask**, you must restart the instance of [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)]. This option is only visible on the 64-bit version of [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)].  
  
## See Also  
 [affinity Input-Output mask Server Configuration Option](../../database-engine/configure-windows/affinity-input-output-mask-server-configuration-option.md)   
 [Monitor Resource Usage (System Monitor)](../../relational-databases/performance-monitor/monitor-resource-usage-system-monitor.md)   
 [Server Configuration Options (SQL Server)](../../database-engine/configure-windows/server-configuration-options-sql-server.md)   
 [sp_configure (Transact-SQL)](../../relational-databases/system-stored-procedures/sp-configure-transact-sql.md)   
 [RECONFIGURE (Transact-SQL)](../../t-sql/language-elements/reconfigure-transact-sql.md)