How many memory slots does the motherboard support and what type of memory can be used?

The motherboard supports 8 memory slots and is compatible with 8-Channel DDR4 UDIMM/RDIMM/3DS RDIMM/LRDIMM.

What is the base and maximum boost clock speed of the AMD Ryzen Threadripper PRO 5965WX processor?

The base clock speed is 3.8 GHz, and the maximum boost clock speed can go up to 4.5 GHz.

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GIGABYTE MC62-G40 AMD Ryzen Threadripper PRO Workstation Board with AMD Threadropper Pro 5965WX Bundle

CPU: Ryzen Threadripper PRO 5965WX, 24-Core/48-Threads, Base Clock 3.8 GHz, Max. Boost Clock Up to 4.5 GHz.
Motherboard:
AMD Ryzen Threadripper PRO 5000WX and 3000WX Processors Socket sWRX8
8-Channel DDR4 UDIMM/RDIMM/3DS RDIMM/LRDIMM 8 x DIMMs
Dual Intel 10GbE and 1GbE LAN Ports
1 x Dedicated Management Port
7 x PCIe 4.0 Slots for Multi-GPU
4x SATA Ports, 3x SlimSAS Ports (PCIe Gen4 or SATA)
Dual M.2 (PCIe Gen4 or SATA) and USB 3.2 Gen2