!!Most PCIe Slots, 

# ASUS PRIME Z390-PRO: Features 6 PCIe, 2-16x and 4-1x and is compatible with Intel LGA 1151 sockets. 128GB Max, 4 DIM,
# ASRock X399 Mining Master: Gaming. 8x DD4 - 128GB Ram Max. 3 PCIe all at 16x.
# EVGA X299 Micro: Features 3 PCIe 2x16, 1x16 and supports Intel Core i7 and i9 processors. 4 DIMM 64GB Max
# ASRock H110 Pro BTC+: Supports up to 13 GPUs, cost-effective, and reliable. 32GB Max, 2 x DDR4 DIMM Slots, 1-16x & 12-1x PCIe
# ASUS B250 Mining Expert: Offers 19 PCIe slots, 18-1x & 1-16x. Max 32GB Ram DDR4.
# Biostar TB250-BTC Pro: Supports up to 12 PCIe. 32GB Max 2 DIMM
# Supermicro X11SPA-IF-D1620-AC - up to 3tb DDR4, 4 PCIe 3.0 x16, 3 PCIe 3.0 x8. Max 4 at x16 otherwise 1x16 and 7 x8  

!!Most Ram Capacity

# ASUS Z10PE-D16 WS: (16 DIMM x 1024GB Max), 4 PCIe 3.0 slots (4 x16 and 2 x8). Multiprocessing x 2. Based on the Intel C612 chipset for Xeon E5 v3/v4 processors. Best one.
# GIGABYTE MW51-HP0: 8 x 64GB or 128GB slots for a max of 1TB, 7 PCIe slots
# Supermicro X11DAi-N: 16 DIMM up 4TB or 2TB (128GB per DIMM), has 6 PCIe. 2 x CPU. Based on the Intel Xeon Scalable platform.
# ASUS WS C621E Sage: 12 x DIMM, Max. 1536GB, DDR4, 6 PCIe 3.0 x16 slots 2 at 8x, 2 x CPU.
# ASRock X570 Taichi: 256GB total (8 x 32GB slots)
# ASRock EP2C621D12-B8: 12 DIMMS 32GB per DIMM, 7 PCIe slots. 
# MSI Creator TRX40: 256GB total (8 x 32GB slots), also compatible with AMD Ryzen Threadripper CPUs.

!!More Choices, 128GB Ram

# MSI MAG B550 TOMAHAWK
# GIGABYTE B550 AORUS ELITE V2
# ASRock B550 Steel Legend
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# MSI MPG B660 Gaming Edge WiFi
# ASUS TUF GAMING B660-PLUS WIFI D4
# GIGABYTE B660 GAMING X AX DDR4
# ASRock X299 Taichi CLX, 256GB Ram
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# ASUS Prime Z690-A WIFI D4 
# ASUS ProArt Z690-CREATOR 10G WIFI DDR4
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Tips
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# Processor: Intel Xeon W-3300 series or AMD Threadripper PRO 7000 series CPU with at least 16 cores.
# Memory: at least 128 GB DDR4 ECC RAM, 256 GB or higher might be beneficial.
# Storage: Opt for fast SSD storage such as NVMe drives with a minimum capacity of 1 TB. NVMe PCIe M.2 SSDs are the fastest.
# Graphics Card(s): NVIDIA RTX 3080, 3080 Ti, 3090, A5000, A6000, or A100 GPUs. Two or more GPUs for efficient parallel processing. The most VRAM.
# Power Supply Unit (PSU): Gold or platinum efficiency certifications to minimize energy loss during conversion.
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# NVIDIA GeForce RTX 3070 Ti: 8 GB GDDR6X
# NVIDIA GeForce RTX 3060 Ti: 8 GB GDDR6
# AMD Radeon RX 6800 XT: 16 GB GDDR6
# AMD Radeon RX 6700 XT: 12 GB GDDR6