Help CPU Xeon-D 1581 E5 v4 speedstep not working

Hi guys,
I need your help.

I have installed Big Sur 11.5.1 on my machine!

CPU: Xeon-D 1581 (Broadwell) 1.8Ghz -- turbo 2.4 Ghz (16 core CPU - 32 Threads)
Mainboard: 8 Series/C220 Chipset Family
Audio: ALC4030 (0x80868C31)
Ram: 32 GB Viper
SSD: Transcend
Video: Ati 7750 (0x683f) CAPE VERDE.

I'm using iMacPro1,1 SMBios trying to exploit 16 core CPU (32 Threads) without success.
My ioreg show plugin-type 0x1 and cf-frequency data in CP00 but CPU frequency is locked to 1.8...

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