Platform Environmental Control Interface；PECI 是什麼!－Kingsman的部落格

平台環境控制介面（Platform Environmental Control Interface；PECI）

Platform Environment Control Interface, abbreviated as PECI, is a thermal management standard introduced in 2006 with the Intel Core 2 Duo microprocessors.

PECI以單線序列式匯流排來支援DTS（Digital Thermal Sensor），相對於溫度二極體（Thermal Diodes；TD）來說，這是一個很重要的進步，而且它以與CPU Vtt相同的電壓來操作。CPU中的DTS會透過PECI介面來報告晶片的溫度，或對內部的風扇控制系統提供溫度數值。

The PECI bus, allowing access to this data from chipset components, is a proprietary single-wire interface with a variable data transfer speed (from 2 kbit/s to 2 Mbit/s).

但在實際應用上，外部晶片都是由 SMB 讀資料，因此，都需要外掛一顆PECI 轉 SMB 的Chip, 後來的 CPU都改以SMB 來讀資料。

一般常見的應用,像是:

BMC acts as a PECI over SMBus master and the SoC SMBus-for-PECI controller acts as a slave PECI proxy controller.

The PECI commands are encapsulated in SMBus packets sent to the CPU.

在CPU設計上, 會將讀跟寫，做在兩個位置上，BMC 透過這兩個位置，進行讀寫動作

The SMBus PECI device is assigned two SMBus Slave Addresses.

• 4Bh = Default SMBus Slave Address for all SMBus Read transactions
• 4Ch = Default SMBus Slave Address for all SMBus Write transactions

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範例：　RdPkgConfig() PECI Proxy Block Write　

0x98/2= 0x4c (device slave address)

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範例：　RdPkgConfig() PECI Proxy Block Read

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範例：　CPU Microcode Update Revision
   CmdData[9] = 0x05; // byte #9 - parameter LSB
   CmdData[10] = 0x00; // byte #10 - parameter MSB (coreID 0-15)
   ret = i2c_master_write( i2cDev, (0x98 >> 1), Cmd, cmdSize);

範例：　MCA Error Source Log

   CmdData[9] = 0x05; // byte #9 - parameter LSB
   CmdData[10] = 0x00; // byte #10 - parameter MSB (coreID 0-15)
   ret = i2c_master_write( i2cDev, (0x98 >> 1), Cmd, cmdSize);