Memory Controller BIOS Request (MC_BIOS_REQ_0_0_0_MCHBAR_PCU) – Offset 5E00 - 1.3 - ID:767625 | 12th Generation Intel® Core™ Processors Datasheet Volume 2 of 2

12th Generation Intel® Core™ Processors Datasheet Volume 2 of 2

ID	Date	Version	Classification
767625	07/13/2023		Public

Memory Controller BIOS Request (MC_BIOS_REQ_0_0_0_MCHBAR_PCU) – Offset 5E00

This register allows BIOS to request Memory Controller clock frequency.

Bit Range	Default	Access	Field Name and Description
31	0x0	RW	RUN/BUSY Bit (RUN_BUSY) This bit indicates that the BIOS request is pending. BIOS sets this bit together with a command in the lower bits of this register. The PCU may only clear this bit after the BIOS request has completed.
30:27	0x0	RW	Request VDDQ TX IccMax (REQ_VDDQ_TX_ICCMAX) Peak current on VDDQTX rail at this clock frequency and gear configuration. Described in 0.25A resolution. Max: 32 * 0.25 = 8A;
26:17	0x0	RW	Request VDDQ TX Voltage (REQ_VDDQ_TX_VOLTAGE) Voltage of the VDDQTX rail at this clock frequency and gear configuration. Described in 5mV resolution.
16:14	0h	RO	Reserved
13:12	0x0	RW	Gear Type (GEAR) 0: Gear1 (Default) - DDR bus clock is the same as QCLK 1: Gear2 - DDR PHY bus clock is double of QCLK 2: Gear4 - DDR PHY bus clock is quad of QCLK
11:8	0x0	RW	Reference Clock Type (MC_PLL_REF) Request Type: 0: MC frequency request for 133MHz Qclk granularity. 1: MC frequency request for 100MHz Qclk granularity. All other values are reserved.
7:0	0x0	RW	MC PLL Ratio (MC_PLL_RATIO) This field holds the memory controller frequency request (QCLK). Each bin is 133/100MHz and not 266/200MHz. This interface replaces the usage of DCLK ratios and Odd Ratio. QCLK frequency is determined by the MC reference clock (MC_FREQ_TYPE) as well as BCLK. Binary Dec DCLK Equation DCLK Freq QCLK Equation QCLK Freq 0000b 0d ------------------------------------ MC PLL - shutdown -------------------------------------------- ... 0011b 3d 3 * 66.66 200.00 MHz 3 * 133.33 400.00 MHz 0100b 4d 4 * 66.66 266.66 MHz 4 * 133.33 533.33 MHz 0101b 5d 5 * 66.66 333.33 MHz 5 * 133.33 666.67 MHz 0110b 6d 6 * 66.66 400.00 MHz 6 * 133.33 800.00 MHz 0111b 7d 7 * 66.66 466.66 MHz 7 * 133.33 933.33 MHz 1000b 8d 8 * 66.66 533.33 MHz 8 * 133.33 1066.67 MHz ...